angular-docs-cn/aio/content/guide/upgrade.md

Upgrading from AngularJS

Angular is the name for the Angular of today and tomorrow. AngularJS is the name for all v1.x versions of Angular.

AngularJS apps are great. Always consider the business case before moving to Angular. An important part of that case is the time and effort to get there. This guide describes the built-in tools for efficiently migrating AngularJS projects over to the Angular platform, a piece at a time.

Some applications will be easier to upgrade than others, and there are many ways to make it easier for yourself. It is possible to prepare and align AngularJS applications with Angular even before beginning the upgrade process. These preparation steps are all about making the code more decoupled, more maintainable, and better aligned with modern development tools. That means in addition to making the upgrade easier, you will also improve the existing AngularJS applications.

One of the keys to a successful upgrade is to do it incrementally, by running the two frameworks side by side in the same application, and porting AngularJS components to Angular one by one. This makes it possible to upgrade even large and complex applications without disrupting other business, because the work can be done collaboratively and spread over a period of time. The upgrade module in Angular has been designed to make incremental upgrading seamless.

Preparation

There are many ways to structure AngularJS applications. When you begin to upgrade these applications to Angular, some will turn out to be much more easy to work with than others. There are a few key techniques and patterns that you can apply to future proof apps even before you begin the migration.

{@a follow-the-angular-styleguide}

Follow the AngularJS Style Guide

The AngularJS Style Guide collects patterns and practices that have been proven to result in cleaner and more maintainable AngularJS applications. It contains a wealth of information about how to write and organize AngularJS code - and equally importantly - how not to write and organize AngularJS code.

Angular is a reimagined version of the best parts of AngularJS. In that sense, its goals are the same as the AngularJS Style Guide's: To preserve the good parts of AngularJS, and to avoid the bad parts. There's a lot more to Angular than just that of course, but this does mean that following the style guide helps make your AngularJS app more closely aligned with Angular.

There are a few rules in particular that will make it much easier to do an incremental upgrade using the Angular upgrade/static module:

• The Rule of 1 states that there should be one component per file. This not only makes components easy to navigate and find, but will also allow us to migrate them between languages and frameworks one at a time. In this example application, each controller, component, service, and filter is in its own source file.

• The Folders-by-Feature Structure and Modularity rules define similar principles on a higher level of abstraction: Different parts of the application should reside in different directories and NgModules.

When an application is laid out feature per feature in this way, it can also be migrated one feature at a time. For applications that don't already look like this, applying the rules in the AngularJS style guide is a highly recommended preparation step. And this is not just for the sake of the upgrade - it is just solid advice in general!

Using a Module Loader

When you break application code down into one component per file, you often end up with a project structure with a large number of relatively small files. This is a much neater way to organize things than a small number of large files, but it doesn't work that well if you have to load all those files to the HTML page with <script> tags. Especially when you also have to maintain those tags in the correct order. That's why it's a good idea to start using a module loader.

Using a module loader such as SystemJS, Webpack, or Browserify allows us to use the built-in module systems of TypeScript or ES2015. You can use the import and export features that explicitly specify what code can and will be shared between different parts of the application. For ES5 applications you can use CommonJS style require and module.exports features. In both cases, the module loader will then take care of loading all the code the application needs in the correct order.

When moving applications into production, module loaders also make it easier to package them all up into production bundles with batteries included.

Migrating to TypeScript

If part of the Angular upgrade plan is to also take TypeScript into use, it makes sense to bring in the TypeScript compiler even before the upgrade itself begins. This means there's one less thing to learn and think about during the actual upgrade. It also means you can start using TypeScript features in your AngularJS code.

Since TypeScript is a superset of ECMAScript 2015, which in turn is a superset of ECMAScript 5, "switching" to TypeScript doesn't necessarily require anything more than installing the TypeScript compiler and renaming files from *.js to *.ts. But just doing that is not hugely useful or exciting, of course. Additional steps like the following can give us much more bang for the buck:

• For applications that use a module loader, TypeScript imports and exports (which are really ECMAScript 2015 imports and exports) can be used to organize code into modules.

• Type annotations can be gradually added to existing functions and variables to pin down their types and get benefits like build-time error checking, great autocompletion support and inline documentation.

• JavaScript features new to ES2015, like arrow functions, lets and consts, default function parameters, and destructuring assignments can also be gradually added to make the code more expressive.

• Services and controllers can be turned into classes. That way they'll be a step closer to becoming Angular service and component classes, which will make life easier after the upgrade.

Using Component Directives

In Angular, components are the main primitive from which user interfaces are built. You define the different portions of the UI as components and compose them into a full user experience.

You can also do this in AngularJS, using component directives. These are directives that define their own templates, controllers, and input/output bindings - the same things that Angular components define. Applications built with component directives are much easier to migrate to Angular than applications built with lower-level features like ng-controller, ng-include, and scope inheritance.

To be Angular compatible, an AngularJS component directive should configure these attributes:

• restrict: 'E'. Components are usually used as elements.
• scope: {} - an isolate scope. In Angular, components are always isolated from their surroundings, and you should do this in AngularJS too.
• bindToController: {}. Component inputs and outputs should be bound to the controller instead of using the $scope.
• controller and controllerAs. Components have their own controllers.
• template or templateUrl. Components have their own templates.

Component directives may also use the following attributes:

• transclude: true/{}, if the component needs to transclude content from elsewhere.
• require, if the component needs to communicate with some parent component's controller.

Component directives should not use the following attributes:

• compile. This will not be supported in Angular.
• replace: true. Angular never replaces a component element with the component template. This attribute is also deprecated in AngularJS.
• priority and terminal. While AngularJS components may use these, they are not used in Angular and it is better not to write code that relies on them.

An AngularJS component directive that is fully aligned with the Angular architecture may look something like this:

AngularJS 1.5 introduces the component API that makes it easier to define component directives like these. It is a good idea to use this API for component directives for several reasons:

• It requires less boilerplate code.
• It enforces the use of component best practices like controllerAs.
• It has good default values for directive attributes like scope and restrict.

The component directive example from above looks like this when expressed using the component API:

Controller lifecycle hook methods $onInit(), $onDestroy(), and $onChanges() are another convenient feature that AngularJS 1.5 introduces. They all have nearly exact equivalents in Angular, so organizing component lifecycle logic around them will ease the eventual Angular upgrade process.

Upgrading with ngUpgrade

The ngUpgrade library in Angular is a very useful tool for upgrading anything but the smallest of applications. With it you can mix and match AngularJS and Angular components in the same application and have them interoperate seamlessly. That means you don't have to do the upgrade work all at once, since there's a natural coexistence between the two frameworks during the transition period.

How ngUpgrade Works

The primary tool provided by ngUpgrade is called the UpgradeModule. This is a module that contains utilities for bootstrapping and managing hybrid applications that support both Angular and AngularJS code.

When you use ngUpgrade, what you're really doing is running both AngularJS and Angular at the same time. All Angular code is running in the Angular framework, and AngularJS code in the AngularJS framework. Both of these are the actual, fully featured versions of the frameworks. There is no emulation going on, so you can expect to have all the features and natural behavior of both frameworks.

What happens on top of this is that components and services managed by one framework can interoperate with those from the other framework. This happens in three main areas: Dependency injection, the DOM, and change detection.

Dependency Injection

Dependency injection is front and center in both AngularJS and Angular, but there are some key differences between the two frameworks in how it actually works.

AngularJS	Angular
Dependency injection tokens are always strings	Tokens [can have different types](guide/dependency-injection). They are often classes. They may also be strings. </td>
There is exactly one injector. Even in multi-module applications, everything is poured into one big namespace. </td> <td> There is a [tree hierarchy of injectors](guide/hierarchical-dependency-injection), with a root injector and an additional injector for each component. </td>

Even accounting for these differences you can still have dependency injection interoperability. The UpgradeModule resolves the differences and makes everything work seamlessly:

• You can make AngularJS services available for injection to Angular code by upgrading them. The same singleton instance of each service is shared between the frameworks. In Angular these services will always be in the root injector and available to all components.

• You can also make Angular services available for injection to AngularJS code by downgrading them. Only services from the Angular root injector can be downgraded. Again, the same singleton instances are shared between the frameworks. When you register a downgraded service, you must explicitly specify a string token that you want to use in AngularJS.

Components and the DOM

In the DOM of a hybrid ngUpgrade application are components and directives from both AngularJS and Angular. These components communicate with each other by using the input and output bindings of their respective frameworks, which ngUpgrade bridges together. They may also communicate through shared injected dependencies, as described above.

The key thing to understand about a hybrid application is that every element in the DOM is owned by exactly one of the two frameworks. The other framework ignores it. If an element is owned by AngularJS, Angular treats it as if it didn't exist, and vice versa.

So normally a hybrid application begins life as an AngularJS application, and it is AngularJS that processes the root template, e.g. the index.html. Angular then steps into the picture when an Angular component is used somewhere in an AngularJS template. That component's template will then be managed by Angular, and it may contain any number of Angular components and directives.

Beyond that, you may interleave the two frameworks. You always cross the boundary between the two frameworks by one of two ways:

1. By using a component from the other framework: An AngularJS template using an Angular component, or an Angular template using an AngularJS component.

2. By transcluding or projecting content from the other framework. ngUpgrade bridges the related concepts of AngularJS transclusion and Angular content projection together.

Whenever you use a component that belongs to the other framework, a switch between framework boundaries occurs. However, that switch only happens to the elements in the template of that component. Consider a situation where you use an Angular component from AngularJS like this:

<a-component></a-component>

The DOM element <a-component> will remain to be an AngularJS managed element, because it's defined in an AngularJS template. That also means you can apply additional AngularJS directives to it, but not Angular directives. It is only in the template of the <a-component> where Angular steps in. This same rule also applies when you use AngularJS component directives from Angular.

Change Detection

The scope.$apply() is how AngularJS detects changes and updates data bindings. After every event that occurs, scope.$apply() gets called. This is done either automatically by the framework, or manually by you.

In Angular things are different. While change detection still occurs after every event, no one needs to call scope.$apply() for that to happen. This is because all Angular code runs inside something called the Angular zone. Angular always knows when the code finishes, so it also knows when it should kick off change detection. The code itself doesn't have to call scope.$apply() or anything like it.

In the case of hybrid applications, the UpgradeModule bridges the AngularJS and Angular approaches. Here's what happens:

• Everything that happens in the application runs inside the Angular zone. This is true whether the event originated in AngularJS or Angular code. The zone triggers Angular change detection after every event.

• The UpgradeModule will invoke the AngularJS $rootScope.$apply() after every turn of the Angular zone. This also triggers AngularJS change detection after every event.

In practice, you do not need to call $apply(), regardless of whether it is in AngularJS on Angular. The UpgradeModule does it for us. You can still call $apply() so there is no need to remove such calls from existing code. Those calls just trigger additional AngularJS change detection checks in a hybrid application.

When you downgrade an Angular component and then use it from AngularJS, the component's inputs will be watched using AngularJS change detection. When those inputs change, the corresponding properties in the component are set. You can also hook into the changes by implementing the OnChanges interface in the component, just like you could if it hadn't been downgraded.

Correspondingly, when you upgrade an AngularJS component and use it from Angular, all the bindings defined for the component directive's scope (or bindToController) will be hooked into Angular change detection. They will be treated as regular Angular inputs. Their values will be written to the upgraded component's scope (or controller) when they change.

Using UpgradeModule with Angular NgModules

Both AngularJS and Angular have their own concept of modules to help organize an application into cohesive blocks of functionality.

Their details are quite different in architecture and implementation. In AngularJS, you add Angular assets to the angular.module property. In Angular, you create one or more classes adorned with an NgModule decorator that describes Angular assets in metadata. The differences blossom from there.

In a hybrid application you run both versions of Angular at the same time. That means that you need at least one module each from both AngularJS and Angular. You will import UpgradeModule inside the NgModule, and then use it for bootstrapping the AngularJS module.

For more information, see NgModules.

Bootstrapping hybrid applications

To bootstrap a hybrid application, you must bootstrap each of the Angular and AngularJS parts of the application. You must bootstrap the Angular bits first and then ask the UpgradeModule to bootstrap the AngularJS bits next.

In an AngularJS application you have a root AngularJS module, which will also be used to bootstrap the AngularJS application.

Pure AngularJS applications can be automatically bootstrapped by using an ng-app directive somewhere on the HTML page. But for hybrid applications, you manually bootstrap via the UpgradeModule. Therefore, it is a good preliminary step to switch AngularJS applications to use the manual JavaScript angular.bootstrap method even before switching them to hybrid mode.

Say you have an ng-app driven bootstrap such as this one:

You can remove the ng-app and ng-strict-di directives from the HTML and instead switch to calling angular.bootstrap from JavaScript, which will result in the same thing:

To begin converting your AngularJS application to a hybrid, you need to load the Angular framework. You can see how this can be done with SystemJS by following the instructions in Setup, selectively copying code from the QuickStart github repository.

You also need to install the @angular/upgrade package via npm install @angular/upgrade --save and add a mapping for the @angular/upgrade/static package:

Next, create an app.module.ts file and add the following NgModule class:

This bare minimum NgModule imports BrowserModule, the module every Angular browser-based app must have. It also imports UpgradeModule from @angular/upgrade/static, which exports providers that will be used for upgrading and downgrading services and components.

In the constructor of the AppModule, use dependency injection to get a hold of the UpgradeModule instance, and use it to bootstrap the AngularJS app in the AppModule.ngDoBootstrap method. The upgrade.bootstrap method takes the exact same arguments as angular.bootstrap:

Note that you do not add a bootstrap declaration to the @NgModule decorator, since AngularJS will own the root template of the application.

Now you can bootstrap AppModule using the platformBrowserDynamic.bootstrapModule method.

Congratulations! You're running a hybrid application! The existing AngularJS code works as before and you're ready to start adding Angular code.

Using Angular Components from AngularJS Code

Once you're running a hybrid app, you can start the gradual process of upgrading code. One of the more common patterns for doing that is to use an Angular component in an AngularJS context. This could be a completely new component or one that was previously AngularJS but has been rewritten for Angular.

Say you have a simple Angular component that shows information about a hero:

If you want to use this component from AngularJS, you need to downgrade it using the downgradeComponent() method. The result is an AngularJS directive, which you can then register in the AngularJS module:

Because HeroDetailComponent is an Angular component, you must also add it to the declarations in the AppModule.

And because this component is being used from the AngularJS module, and is an entry point into the Angular application, you must add it to the entryComponents for the NgModule.

All Angular components, directives and pipes must be declared in an NgModule.

The net result is an AngularJS directive called heroDetail, that you can use like any other directive in AngularJS templates.

Note that this AngularJS is an element directive (restrict: 'E') called heroDetail. An AngularJS element directive is matched based on its name. The selector metadata of the downgraded Angular component is ignored.

Most components are not quite this simple, of course. Many of them have inputs and outputs that connect them to the outside world. An Angular hero detail component with inputs and outputs might look like this:

These inputs and outputs can be supplied from the AngularJS template, and the downgradeComponent() method takes care of wiring them up:

Note that even though you are in an AngularJS template, you're using Angular attribute syntax to bind the inputs and outputs. This is a requirement for downgraded components. The expressions themselves are still regular AngularJS expressions.

Use kebab-case for downgraded component attributes

There's one notable exception to the rule of using Angular attribute syntax for downgraded components. It has to do with input or output names that consist of multiple words. In Angular, you would bind these attributes using camelCase:

[myHero]="hero"

But when using them from AngularJS templates, you must use kebab-case:

[my-hero]="hero"

The $event variable can be used in outputs to gain access to the object that was emitted. In this case it will be the Hero object, because that is what was passed to this.deleted.emit().

Since this is an AngularJS template, you can still use other AngularJS directives on the element, even though it has Angular binding attributes on it. For example, you can easily make multiple copies of the component using ng-repeat:

Using AngularJS Component Directives from Angular Code

So, you can write an Angular component and then use it from AngularJS code. This is useful when you start to migrate from lower-level components and work your way up. But in some cases it is more convenient to do things in the opposite order: To start with higher-level components and work your way down. This too can be done using the UpgradeModule. You can upgrade AngularJS component directives and then use them from Angular.

Not all kinds of AngularJS directives can be upgraded. The directive really has to be a component directive, with the characteristics described in the preparation guide above. The safest bet for ensuring compatibility is using the component API introduced in AngularJS 1.5.

A simple example of an upgradable component is one that just has a template and a controller:

You can upgrade this component to Angular using the UpgradeComponent class. By creating a new Angular directive that extends UpgradeComponent and doing a super call inside its constructor, you have a fully upgraded AngularJS component to be used inside Angular. All that is left is to add it to AppModule's declarations array.

Upgraded components are Angular directives, instead of components, because Angular is unaware that AngularJS will create elements under it. As far as Angular knows, the upgraded component is just a directive - a tag - and Angular doesn't have to concern itself with its children.

An upgraded component may also have inputs and outputs, as defined by the scope/controller bindings of the original AngularJS component directive. When you use the component from an Angular template, provide the inputs and outputs using Angular template syntax, observing the following rules:

	Binding definition	Template syntax
Attribute binding	`myAttribute: '@myAttribute'` </td> <td> `<my-component myAttribute="value">` </td>
Expression binding	`myOutput: '&myOutput'` </td> <td> `<my-component (myOutput)="action()">` </td>
One-way binding	`myValue: '<myValue'` </td> <td> `<my-component [myValue]="anExpression">` </td>
Two-way binding	`myValue: '=myValue'` </td> <td> As a two-way binding: `<my-component [(myValue)]="anExpression">`. Since most AngularJS two-way bindings actually only need a one-way binding in practice, `<my-component [myValue]="anExpression">` is often enough. </td>

For example, imagine a hero detail AngularJS component directive with one input and one output:

You can upgrade this component to Angular, annotate inputs and outputs in the upgrade directive, and then provide the input and output using Angular template syntax:

Projecting AngularJS Content into Angular Components

When you are using a downgraded Angular component from an AngularJS template, the need may arise to transclude some content into it. This is also possible. While there is no such thing as transclusion in Angular, there is a very similar concept called content projection. The UpgradeModule is able to make these two features interoperate.

Angular components that support content projection make use of an <ng-content> tag within them. Here's an example of such a component:

When using the component from AngularJS, you can supply contents for it. Just like they would be transcluded in AngularJS, they get projected to the location of the <ng-content> tag in Angular:

When AngularJS content gets projected inside an Angular component, it still remains in "AngularJS land" and is managed by the AngularJS framework.

Transcluding Angular Content into AngularJS Component Directives

Just as you can project AngularJS content into Angular components, you can transclude Angular content into AngularJS components, whenever you are using upgraded versions from them.

When an AngularJS component directive supports transclusion, it may use the ng-transclude directive in its template to mark the transclusion point:

If you upgrade this component and use it from Angular, you can populate the component tag with contents that will then get transcluded:

Making AngularJS Dependencies Injectable to Angular

When running a hybrid app, you may encounter situations where you need to inject some AngularJS dependencies into your Angular code. Maybe you have some business logic still in AngularJS services. Maybe you want access to AngularJS's built-in services like $location or $timeout.

In these situations, it is possible to upgrade an AngularJS provider to Angular. This makes it possible to then inject it somewhere in Angular code. For example, you might have a service called HeroesService in AngularJS:

You can upgrade the service using a Angular factory provider that requests the service from the AngularJS $injector.

Many developers prefer to declare the factory provider in a separate ajs-upgraded-providers.ts file so that they are all together, making it easier to reference them, create new ones and delete them once the upgrade is over.

It's also recommended to export the heroesServiceFactory function so that Ahead-of-Time compilation can pick it up.

You can then inject it in Angular using its class as a type annotation:

In this example you upgraded a service class. You can use a TypeScript type annotation when you inject it. While it doesn't affect how the dependency is handled, it enables the benefits of static type checking. This is not required though, and any AngularJS service, factory, or provider can be upgraded.

Making Angular Dependencies Injectable to AngularJS

In addition to upgrading AngularJS dependencies, you can also downgrade Angular dependencies, so that you can use them from AngularJS. This can be useful when you start migrating services to Angular or creating new services in Angular while retaining components written in AngularJS.

For example, you might have an Angular service called Heroes:

Again, as with Angular components, register the provider with the NgModule by adding it to the module's providers list.

Now wrap the Angular Heroes in an AngularJS factory function using downgradeInjectable() and plug the factory into an AngularJS module. The name of the AngularJS dependency is up to you:

After this, the service is injectable anywhere in AngularJS code:

Using Ahead-of-time compilation with hybrid apps

You can take advantage of Ahead-of-time (AOT) compilation on hybrid apps just like on any other Angular application. The setup for an hybrid app is mostly the same as described in the Ahead-of-time Compilation chapter save for differences in index.html and main-aot.ts

The index.html will likely have script tags loading AngularJS files, so the index.html for AOT must also load those files. An easy way to copy them is by adding each to the copy-dist-files.js file.

You'll need to use the generated AppModuleFactory, instead of the original AppModule to bootstrap the hybrid app:

And that's all you need do to get the full benefit of AOT for Angular apps!

PhoneCat Upgrade Tutorial

In this section, you'll learn to prepare and upgrade an application with ngUpgrade. The example app is Angular PhoneCat from the original AngularJS tutorial, which is where many of us began our Angular adventures. Now you'll see how to bring that application to the brave new world of Angular.

During the process you'll learn how to apply the steps outlined in the preparation guide. You'll align the application with Angular and also start writing in TypeScript.

To follow along with the tutorial, clone the angular-phonecat repository and apply the steps as you go.

In terms of project structure, this is where the work begins:

angular-phonecat

bower.json

karma.conf.js

package.json

app

core

checkmark

checkmark.filter.js

checkmark.filter.spec.js

phone

phone.module.js

phone.service.js

phone.service.spec.js

core.module.js

phone-detail

phone-detail.component.js

phone-detail.component.spec.js

phone-detail.module.js

phone-detail.template.html

phone-list

phone-list.component.js

phone-list.component.spec.js

phone-list.module.js

phone-list.template.html

img

...

phones

...

app.animations.js

app.config.js

app.css

app.module.js

index.html

e2e-tests

protractor-conf.js

scenarios.js

This is actually a pretty good starting point. The code uses the AngularJS 1.5 component API and the organization follows the AngularJS Style Guide, which is an important preparation step before a successful upgrade.

• Each component, service, and filter is in its own source file, as per the Rule of 1.

• The core, phone-detail, and phone-list modules are each in their own subdirectory. Those subdirectories contain the JavaScript code as well as the HTML templates that go with each particular feature. This is in line with the Folders-by-Feature Structure and Modularity rules.

• Unit tests are located side-by-side with application code where they are easily found, as described in the rules for Organizing Tests.

Switching to TypeScript

Since you're going to be writing Angular code in TypeScript, it makes sense to bring in the TypeScript compiler even before you begin upgrading.

You'll also start to gradually phase out the Bower package manager in favor of NPM, installing all new dependencies using NPM, and eventually removing Bower from the project.

Begin by installing TypeScript to the project.

npm i typescript --save-dev

Install type definitions for the existing libraries that you're using but that don't come with prepackaged types: AngularJS and the Jasmine unit test framework.

npm install @types/jasmine @types/angular @types/angular-animate @types/angular-cookies @types/angular-mocks @types/angular-resource @types/angular-route @types/angular-sanitize --save-dev

You should also configure the TypeScript compiler with a tsconfig.json in the project directory as described in the TypeScript Configuration guide. The tsconfig.json file tells the TypeScript compiler how to turn your TypeScript files into ES5 code bundled into CommonJS modules.

Finally, you should add some npm scripts in package.json to compile the TypeScript files to JavaScript (based on the tsconfig.json configuration file):

"script": { "tsc": "tsc", "tsc:w": "tsc -w", ...

Now launch the TypeScript compiler from the command line in watch mode:

npm run tsc:w

Keep this process running in the background, watching and recompiling as you make changes.

Next, convert your current JavaScript files into TypeScript. Since TypeScript is a super-set of ECMAScript 2015, which in turn is a super-set of ECMAScript 5, you can simply switch the file extensions from .js to .ts and everything will work just like it did before. As the TypeScript compiler runs, it emits the corresponding .js file for every .ts file and the compiled JavaScript is what actually gets executed. If you start the project HTTP server with npm start, you should see the fully functional application in your browser.

Now that you have TypeScript though, you can start benefiting from some of its features. There's a lot of value the language can provide to AngularJS applications.

For one thing, TypeScript is a superset of ES2015. Any app that has previously been written in ES5 - like the PhoneCat example has - can with TypeScript start incorporating all of the JavaScript features that are new to ES2015. These include things like lets and consts, arrow functions, default function parameters, and destructuring assignments.

Another thing you can do is start adding type safety to your code. This has actually partially already happened because of the AngularJS typings you installed. TypeScript are checking that you are calling AngularJS APIs correctly when you do things like register components to Angular modules.

But you can also start adding type annotations to get even more out of TypeScript's type system. For instance, you can annotate the checkmark filter so that it explicitly expects booleans as arguments. This makes it clearer what the filter is supposed to do.

In the Phone service, you can explicitly annotate the $resource service dependency as an angular.resource.IResourceService - a type defined by the AngularJS typings.

You can apply the same trick to the application's route configuration file in app.config.ts, where you are using the location and route services. By annotating them accordingly TypeScript can verify you're calling their APIs with the correct kinds of arguments.

The AngularJS 1.x type definitions you installed are not officially maintained by the Angular team, but are quite comprehensive. It is possible to make an AngularJS 1.x application fully type-annotated with the help of these definitions.

If this is something you wanted to do, it would be a good idea to enable the noImplicitAny configuration option in tsconfig.json. This would cause the TypeScript compiler to display a warning when there's any code that does not yet have type annotations. You could use it as a guide to inform us about how close you are to having a fully annotated project.

Another TypeScript feature you can make use of is classes. In particular, you can turn component controllers into classes. That way they'll be a step closer to becoming Angular component classes, which will make life easier once you upgrade.

AngularJS expects controllers to be constructor functions. That's exactly what ES2015/TypeScript classes are under the hood, so that means you can just plug in a class as a component controller and AngularJS will happily use it.

Here's what the new class for the phone list component controller looks like:

What was previously done in the controller function is now done in the class constructor function. The dependency injection annotations are attached to the class using a static property $inject. At runtime this becomes the PhoneListController.$inject property.

The class additionally declares three members: The array of phones, the name of the current sort key, and the search query. These are all things you have already been attaching to the controller but that weren't explicitly declared anywhere. The last one of these isn't actually used in the TypeScript code since it's only referred to in the template, but for the sake of clarity you should define all of the controller members.

In the Phone detail controller, you'll have two members: One for the phone that the user is looking at and another for the URL of the currently displayed image:

This makes the controller code look a lot more like Angular already. You're all set to actually introduce Angular into the project.

If you had any AngularJS services in the project, those would also be a good candidate for converting to classes, since like controllers, they're also constructor functions. But you only have the Phone factory in this project, and that's a bit special since it's an ngResource factory. So you won't be doing anything to it in the preparation stage. You'll instead turn it directly into an Angular service.

Installing Angular

Having completed the preparation work, get going with the Angular upgrade of PhoneCat. You'll do this incrementally with the help of ngUpgrade that comes with Angular. By the time you're done, you'll be able to remove AngularJS from the project completely, but the key is to do this piece by piece without breaking the application.

The project also contains some animations. You won't upgrade them in this version of the guide. Turn to the Angular animations guide to learn about that.

Install Angular into the project, along with the SystemJS module loader. Take a look at the results of the Setup instructions and get the following configurations from there:

• Add Angular and the other new dependencies to package.json
• The SystemJS configuration file systemjs.config.js to the project root directory.

Once these are done, run:

npm install

Soon you can load Angular dependencies into the application via index.html, but first you need to do some directory path adjustments. You'll need to load files from node_modules and the project root instead of from the /app directory as you've been doing to this point.

Move the app/index.html file to the project root directory. Then change the development server root path in package.json to also point to the project root instead of app:

"start": "http-server ./ -a localhost -p 8000 -c-1",

Now you're able to serve everything from the project root to the web browser. But you do not want to have to change all the image and data paths used in the application code to match the development setup. For that reason, you'll add a <base> tag to index.html, which will cause relative URLs to be resolved back to the /app directory:

Now you can load Angular via SystemJS. You'll add the Angular polyfills and the SystemJS config to the end of the <head> section, and then you'll use System.import to load the actual application:

You also need to make a couple of adjustments to the systemjs.config.js file installed during setup.

Point the browser to the project root when loading things through SystemJS, instead of using the <base> URL.

Install the upgrade package via npm install @angular/upgrade --save and add a mapping for the @angular/upgrade/static package.

Creating the AppModule

Now create the root NgModule class called AppModule. There is already a file named app.module.ts that holds the AngularJS module. Rename it to app.module.ajs.ts and update the corresponding script name in the index.html as well. The file contents remain:

Now create a new app.module.ts with the minimum NgModule class:

Bootstrapping a hybrid PhoneCat

Next, you'll bootstrap the application as a hybrid application that supports both AngularJS and Angular components. After that, you can start converting the individual pieces to Angular.

The application is currently bootstrapped using the AngularJS ng-app directive attached to the <html> element of the host page. This will no longer work in the hybrid app. Switch to the ngUpgrade bootstrap method instead.

First, remove the ng-app attribute from index.html. Then import UpgradeModule in the AppModule, and override its ngDoBootstrap method:

Note that you are bootstrapping the AngularJS module from inside ngDoBootstrap. The arguments are the same as you would pass to angular.bootstrap if you were manually bootstrapping AngularJS: the root element of the application; and an array of the AngularJS 1.x modules that you want to load.

Finally, bootstrap the AppModule in src/main.ts. This file has been configured as the application entrypoint in systemjs.config.js, so it is already being loaded by the browser.

Now you're running both AngularJS and Angular at the same time. That's pretty exciting! You're not running any actual Angular components yet. That's next.

Why declare angular as angular.IAngularStatic?

@types/angular is declared as a UMD module, and due to the way UMD typings work, once you have an ES6 import statement in a file all UMD typed modules must also be imported via import statements instead of being globally available.

AngularJS is currently loaded by a script tag in index.html, which means that the whole app has access to it as a global and uses the same instance of the angular variable. If you used import * as angular from 'angular' instead, you'd also have to load every file in the AngularJS app to use ES2015 modules in order to ensure AngularJS was being loaded correctly.

This is a considerable effort and it often isn't worth it, especially since you are in the process of moving your code to Angular. Instead, declare angular as angular.IAngularStatic to indicate it is a global variable and still have full typing support.

Upgrading the Phone service

The first piece you'll port over to Angular is the Phone service, which resides in app/core/phone/phone.service.ts and makes it possible for components to load phone information from the server. Right now it's implemented with ngResource and you're using it for two things:

• For loading the list of all phones into the phone list component.
• For loading the details of a single phone into the phone detail component.

You can replace this implementation with an Angular service class, while keeping the controllers in AngularJS land.

In the new version, you import the Angular HTTP module and call its Http service instead of ngResource.

Re-open the app.module.ts file, import and add HttpModule to the imports array of the AppModule:

Now you're ready to upgrade the Phone service itself. Replace the ngResource-based service in phone.service.ts with a TypeScript class decorated as @Injectable:

The @Injectable decorator will attach some dependency injection metadata to the class, letting Angular know about its dependencies. As described by the Dependency Injection Guide, this is a marker decorator you need to use for classes that have no other Angular decorators but still need to have their dependencies injected.

In its constructor the class expects to get the Http service. It will be injected to it and it is stored as a private field. The service is then used in the two instance methods, one of which loads the list of all phones, and the other loads the details of a specified phone:

The methods now return observables of type PhoneData and PhoneData[]. This is a type you don't have yet. Add a simple interface for it:

@angular/upgrade/static has a downgradeInjectable method for the purpose of making Angular services available to AngularJS code. Use it to plug in the Phone service:

Here's the full, final code for the service:

Notice that you're importing the map operator of the RxJS Observable separately. Do this for every RxJS operator.

The new Phone service has the same features as the original, ngResource-based service. Because it's an Angular service, you register it with the NgModule providers:

Now that you are loading phone.service.ts through an import that is resolved by SystemJS, you should remove the <script> tag for the service from index.html. This is something you'll do to all components as you upgrade them. Simultaneously with the AngularJS to Angular upgrade you're also migrating code from scripts to modules.

At this point, you can switch the two components to use the new service instead of the old one. While you $inject it as the downgraded phone factory, it's really an instance of the Phone class and you annotate its type accordingly:

Now there are two AngularJS components using an Angular service! The components don't need to be aware of this, though the fact that the service returns observables and not promises is a bit of a giveaway. In any case, what you've achieved is a migration of a service to Angular without having to yet migrate the components that use it.

You could use the toPromise method of Observable to turn those observables into promises in the service. In many cases that reduce the number of changes to the component controllers.

Upgrading Components

Upgrade the AngularJS components to Angular components next. Do it one component at a time while still keeping the application in hybrid mode. As you make these conversions, you'll also define your first Angular pipes.

Look at the phone list component first. Right now it contains a TypeScript controller class and a component definition object. You can morph this into an Angular component by just renaming the controller class and turning the AngularJS component definition object into an Angular @Component decorator. You can then also remove the static $inject property from the class:

The selector attribute is a CSS selector that defines where on the page the component should go. In AngularJS you do matching based on component names, but in Angular you have these explicit selectors. This one will match elements with the name phone-list, just like the AngularJS version did.

Now convert the template of this component into Angular syntax. The search controls replace the AngularJS $ctrl expressions with Angular's two-way [(ngModel)] binding syntax:

Replace the list's ng-repeat with an *ngFor as described in the Template Syntax page. Replace the image tag's ng-src with a binding to the native src property.

No Angular filter or orderBy filters

The built-in AngularJS filter and orderBy filters do not exist in Angular, so you need to do the filtering and sorting yourself.

You replaced the filter and orderBy filters with bindings to the getPhones() controller method, which implements the filtering and ordering logic inside the component itself.

Now you need to downgrade the Angular component so you can use it in AngularJS. Instead of registering a component, you register a phoneList directive, a downgraded version of the Angular component.

The as angular.IDirectiveFactory cast tells the TypeScript compiler that the return value of the downgradeComponent method is a directive factory.

The new PhoneListComponent uses the Angular ngModel directive, located in the FormsModule. Add the FormsModule to NgModule imports, declare the new PhoneListComponent and finally add it to entryComponents since you downgraded it:

Remove the <script> tag for the phone list component from index.html.

Now set the remaining phone-detail.component.ts as follows:

This is similar to the phone list component. The new wrinkle is the RouteParams type annotation that identifies the routeParams dependency.

The AngularJS injector has an AngularJS router dependency called $routeParams, which was injected into PhoneDetails when it was still an AngularJS controller. You intend to inject it into the new PhoneDetailsComponent.

Unfortunately, AngularJS dependencies are not automatically available to Angular components. You must upgrade this service via a factory provider to make $routeParams an Angular injectable. Do that in a new file called ajs-upgraded-providers.ts and import it in app.module.ts:

Convert the phone detail component template into Angular syntax as follows:

There are several notable changes here:

• You've removed the $ctrl. prefix from all expressions.

• You've replaced ng-src with property bindings for the standard src property.

• You're using the property binding syntax around ng-class. Though Angular does have a very similar ngClass as AngularJS does, its value is not magically evaluated as an expression. In Angular, you always specify in the template when an attribute's value is a property expression, as opposed to a literal string.

• You've replaced ng-repeats with *ngFors.

• You've replaced ng-click with an event binding for the standard click.

• You've wrapped the whole template in an ngIf that causes it only to be rendered when there is a phone present. You need this because when the component first loads, you don't have phone yet and the expressions will refer to a non-existing value. Unlike in AngularJS, Angular expressions do not fail silently when you try to refer to properties on undefined objects. You need to be explicit about cases where this is expected.

Add PhoneDetailComponent component to the NgModule declarations and entryComponents:

You should now also remove the phone detail component <script> tag from index.html.

Add the CheckmarkPipe

The AngularJS directive had a checkmark filter. Turn that into an Angular pipe.

There is no upgrade method to convert filters into pipes. You won't miss it. It's easy to turn the filter function into an equivalent Pipe class. The implementation is the same as before, repackaged in the transform method. Rename the file to checkmark.pipe.ts to conform with Angular conventions:

Now import and declare the newly created pipe and remove the filter <script> tag from index.html:

AOT compile the hybrid app

To use AOT with a hybrid app, you have to first set it up like any other Angular application, as shown in the Ahead-of-time Compilation chapter.

Then change main-aot.ts to bootstrap the AppComponentFactory that was generated by the AOT compiler:

You need to load all the AngularJS files you already use in index.html in aot/index.html as well:

These files need to be copied together with the polyfills. The files the application needs at runtime, like the .json phone lists and images, also need to be copied.

Install fs-extra via npm install fs-extra --save-dev for better file copying, and change copy-dist-files.js to the following:

And that's all you need to use AOT while upgrading your app!

Adding The Angular Router And Bootstrap

At this point, you've replaced all AngularJS application components with their Angular counterparts, even though you're still serving them from the AngularJS router.

Add the Angular router

Angular has an all-new router.

Like all routers, it needs a place in the UI to display routed views. For Angular that's the <router-outlet> and it belongs in a root component at the top of the applications component tree.

You don't yet have such a root component, because the app is still managed as an AngularJS app. Create a new app.component.ts file with the following AppComponent class:

It has a simple template that only includes the `. This component just renders the contents of the active route and nothing else.

The selector tells Angular to plug this root component into the <phonecat-app> element on the host web page when the application launches.

Add this <phonecat-app> element to the index.html. It replaces the old AngularJS ng-view directive:

Create the Routing Module

A router needs configuration whether it's the AngularJS or Angular or any other router.

The details of Angular router configuration are best left to the Routing documentation which recommends that you create a NgModule dedicated to router configuration (called a Routing Module).

This module defines a routes object with two routes to the two phone components and a default route for the empty path. It passes the routes to the RouterModule.forRoot method which does the rest.

A couple of extra providers enable routing with "hash" URLs such as #!/phones instead of the default "push state" strategy.

Now update the AppModule to import this AppRoutingModule and also the declare the root AppComponent as the bootstrap component. That tells Angular that it should bootstrap the app with the root AppComponent and insert its view into the host web page.

You must also remove the bootstrap of the AngularJS module from ngDoBootstrap() in app.module.ts and the UpgradeModule import.

And since you are routing to PhoneListComponent and PhoneDetailComponent directly rather than using a route template with a <phone-list> or <phone-detail> tag, you can do away with their Angular selectors as well.

Generate links for each phone

You no longer have to hardcode the links to phone details in the phone list. You can generate data bindings for each phone's id to the routerLink directive and let that directive construct the appropriate URL to the PhoneDetailComponent:

See the Routing page for details.

Use route parameters

The Angular router passes route parameters differently. Correct the PhoneDetail component constructor to expect an injected ActivatedRoute object. Extract the phoneId from the ActivatedRoute.snapshot.params and fetch the phone data as before:

You are now running a pure Angular application!

Say Goodbye to AngularJS

It is time to take off the training wheels and let the application begin its new life as a pure, shiny Angular app. The remaining tasks all have to do with removing code - which of course is every programmer's favorite task!

The application is still bootstrapped as a hybrid app. There's no need for that anymore.

Switch the bootstrap method of the application from the UpgradeModule to the Angular way.

If you haven't already, remove all references to the UpgradeModule from app.module.ts, as well as any factory provider for AngularJS services, and the app/ajs-upgraded-providers.ts file.

Also remove any downgradeInjectable() or downgradeComponent() you find, together with the associated AngularJS factory or directive declarations. Since you no longer have downgraded components, you no longer list them in entryComponents.

You may also completely remove the following files. They are AngularJS module configuration files and not needed in Angular:

• app/app.module.ajs.ts
• app/app.config.ts
• app/core/core.module.ts
• app/core/phone/phone.module.ts
• app/phone-detail/phone-detail.module.ts
• app/phone-list/phone-list.module.ts

The external typings for AngularJS may be uninstalled as well. The only ones you still need are for Jasmine and Angular polyfills. The @angular/upgrade package and its mapping in systemjs.config.js can also go.

npm uninstall @angular/upgrade --save npm uninstall @types/angular @types/angular-animate @types/angular-cookies @types/angular-mocks @types/angular-resource @types/angular-route @types/angular-sanitize --save-dev

Finally, from index.html, remove all references to AngularJS scripts and jQuery. When you're done, this is what it should look like:

That is the last you'll see of AngularJS! It has served us well but now it's time to say goodbye.

Appendix: Upgrading PhoneCat Tests

Tests can not only be retained through an upgrade process, but they can also be used as a valuable safety measure when ensuring that the application does not break during the upgrade. E2E tests are especially useful for this purpose.

E2E Tests

The PhoneCat project has both E2E Protractor tests and some Karma unit tests in it. Of these two, E2E tests can be dealt with much more easily: By definition, E2E tests access the application from the outside by interacting with the various UI elements the app puts on the screen. E2E tests aren't really that concerned with the internal structure of the application components. That also means that, although you modify the project quite a bit during the upgrade, the E2E test suite should keep passing with just minor modifications. You didn't change how the application behaves from the user's point of view.

During TypeScript conversion, there is nothing to do to keep E2E tests working. But when you change the bootstrap to that of a Hybrid app, you must make a few changes.

Update the protractor-conf.js to sync with hybrid apps:

ng12Hybrid: true

When you start to upgrade components and their templates to Angular, you'll make more changes because the E2E tests have matchers that are specific to AngularJS. For PhoneCat you need to make the following changes in order to make things work with Angular:

Previous code	New code	Notes
`by.repeater('phone in $ctrl.phones').column('phone.name')` </td> <td> `by.css('.phones .name')` </td> <td> The repeater matcher relies on AngularJS `ng-repeat` </td>
`by.repeater('phone in $ctrl.phones')` </td> <td> `by.css('.phones li')` </td> <td> The repeater matcher relies on AngularJS `ng-repeat` </td>
`by.model('$ctrl.query')` </td> <td> `by.css('input')` </td> <td> The model matcher relies on AngularJS `ng-model` </td>
`by.model('$ctrl.orderProp')` </td> <td> `by.css('select')` </td> <td> The model matcher relies on AngularJS `ng-model` </td>
`by.binding('$ctrl.phone.name')` </td> <td> `by.css('h1')` </td> <td> The binding matcher relies on AngularJS data binding </td>

When the bootstrap method is switched from that of UpgradeModule to pure Angular, AngularJS ceases to exist on the page completely. At this point, you need to tell Protractor that it should not be looking for an AngularJS app anymore, but instead it should find Angular apps from the page.

Replace the ng12Hybrid previously added with the following in protractor-conf.js:

useAllAngular2AppRoots: true,

Also, there are a couple of Protractor API calls in the PhoneCat test code that are using the AngularJS $location service under the hood. As that service is no longer present after the upgrade, replace those calls with ones that use WebDriver's generic URL APIs instead. The first of these is the redirection spec:

And the second is the phone links spec:

Unit Tests

For unit tests, on the other hand, more conversion work is needed. Effectively they need to be upgraded along with the production code.

During TypeScript conversion no changes are strictly necessary. But it may be a good idea to convert the unit test code into TypeScript as well.

For instance, in the phone detail component spec, you can use ES2015 features like arrow functions and block-scoped variables and benefit from the type definitions of the AngularJS services you're consuming:

Once you start the upgrade process and bring in SystemJS, configuration changes are needed for Karma. You need to let SystemJS load all the new Angular code, which can be done with the following kind of shim file:

The shim first loads the SystemJS configuration, then Angular's test support libraries, and then the application's spec files themselves.

Karma configuration should then be changed so that it uses the application root dir as the base directory, instead of app.

Once done, you can load SystemJS and other dependencies, and also switch the configuration for loading application files so that they are not included to the page by Karma. You'll let the shim and SystemJS load them.

Since the HTML templates of Angular components will be loaded as well, you must help Karma out a bit so that it can route them to the right paths:

The unit test files themselves also need to be switched to Angular when their production counterparts are switched. The specs for the checkmark pipe are probably the most straightforward, as the pipe has no dependencies:

The unit test for the phone service is a bit more involved. You need to switch from the mocked-out AngularJS $httpBackend to a mocked-out Angular Http backend.

For the component specs, you can mock out the Phone service itself, and have it provide canned phone data. You use Angular's component unit testing APIs for both components.

Finally, revisit both of the component tests when you switch to the Angular router. For the details component, provide a mock of Angular ActivatedRoute object instead of using the AngularJS $routeParams.

And for the phone list component, a few adjustments to the router make the RouteLink directives work.