103 lines
3.9 KiB
Markdown
103 lines
3.9 KiB
Markdown
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@title
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Set the Document Title
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@intro
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Setting the document or window title using the Title service.
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@description
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{@a top}
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Our app should be able to make the browser title bar say whatever we want it to say.
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This cookbook explains how to do it.**See the <live-example name="cb-set-document-title"></live-example>**.
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<table>
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<tr>
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<td>
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To see the browser title bar change in the live example,
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open it again in the Plunker editor by clicking the icon in the upper right,
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then pop out the preview window by clicking the blue 'X' button in the upper right corner.
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</td>
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<td>
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<img src='/resources/images/devguide/plunker-switch-to-editor-button.png' width="200px" height="70px" alt="pop out the window" align="right"> </img> <br> </br> <img src='/resources/images/devguide/plunker-separate-window-button.png' width="200px" height="47px" alt="pop out the window" align="right"> </img>
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</td>
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</tr>
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</table>
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## The problem with *<title>*
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The obvious approach is to bind a property of the component to the HTML `<title>` like this:
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<code-example format=''>
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<title>{{This_Does_Not_Work}}</title>
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</code-example>
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Sorry but that won't work.
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The root component of our application is an element contained within the `<body>` tag.
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The HTML `<title>` is in the document `<head>`, outside the body, making it inaccessible to Angular data binding.
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We could grab the browser `document` object and set the title manually.
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That's dirty and undermines our chances of running the app outside of a browser someday.
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Running your app outside a browser means that you can take advantage of server-side
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pre-rendering for near-instant first app render times and for SEO. It means you could run from
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inside a Web Worker to improve your app's responsiveness by using multiple threads. And it
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means that you could run your app inside Electron.js or Windows Universal to deliver it to the desktop.
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## Use the *Title* service
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Fortunately, Angular bridges the gap by providing a `Title` service as part of the *Browser platform*.
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The [Title](../api/platform-browser/index/Title-class.html) service is a simple class that provides an API
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for getting and setting the current HTML document title:
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* `getTitle() : string` — Gets the title of the current HTML document.
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* `setTitle( newTitle : string )` — Sets the title of the current HTML document.
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Let's inject the `Title` service into the root `AppComponent` and expose a bindable `setTitle` method that calls it:
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{@example 'cb-set-document-title/ts/src/app/app.component.ts' region='class'}
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We bind that method to three anchor tags and, voilà!
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<figure class='image-display'>
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<img src="/resources/images/cookbooks/set-document-title/set-title-anim.gif" alt="Set title"> </img>
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</figure>
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Here's the complete solution
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<md-tab-group>
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<md-tab label="src/main.ts">
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{@example 'cb-set-document-title/ts/src/main.ts'}
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</md-tab>
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<md-tab label="src/app/app.module.ts">
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{@example 'cb-set-document-title/ts/src/app/app.module.ts'}
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</md-tab>
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<md-tab label="src/app/app.component.ts">
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{@example 'cb-set-document-title/ts/src/app/app.component.ts'}
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</md-tab>
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</md-tab-group>
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## Why we provide the *Title* service in *bootstrap*
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We generally recommended providing application-wide services in the root application component, `AppComponent`.
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Here we recommend registering the title service during bootstrapping,
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a location we reserve for configuring the runtime Angular environment.
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That's exactly what we're doing.
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The `Title` service is part of the Angular *browser platform*.
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If we bootstrap our application into a different platform,
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we'll have to provide a different `Title` service that understands the concept of a "document title" for that specific platform.
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Ideally the application itself neither knows nor cares about the runtime environment.[Back to top](#top)
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