# Zone.js's support for standard apis

Zone.js patched most standard APIs such as DOM event listeners, XMLHttpRequest in Browser, EventEmitter and fs API in Node.js so they can be in zone.
  
In this document, all patched API are listed. 

For non-standard APIs, please see [NON-STANDARD-APIS.md](NON-STANDARD-APIS.md)
 
## Patch Mechanisms

There are several patch mechanisms

- wrap: makes callbacks run in zones, and makes applications able to receive onInvoke and onIntercept callbacks
- Task: just like in the JavaScript VM, applications can receive onScheduleTask, onInvokeTask, onCancelTask and onHasTask callbacks
  1. MacroTask
  2. MicroTask
  3. EventTask
  
Some APIs which should be treated as Tasks, but are currently still patched in the wrap way. These will be patched as Tasks soon.
 
## Browser 

Web APIs

| API | Patch Mechanism | Others |
| --- | --- | --- |
| setTimeout/clearTimeout | MacroTask | app can get handlerId, interval, args, isPeriodic(false) through task.data |
| setImmediate/clearImmediate | MacroTask | same with setTimeout |
| setInterval/clearInterval | MacroTask | isPeriodic is true, so setInterval will not trigger onHasTask callback | 
| requestAnimationFrame/cancelAnimationFrame | MacroTask |  |
| mozRequestAnimationFrame/mozCancelAnimationFrame | MacroTask |  |
| webkitRequestAnimationFrame/webkitCancelAnimationFrame | MacroTask |  |
| alert | wrap |  |
| prompt | wrap |  |
| confirm | wrap |  |
| Promise | MicroTask |  |
| EventTarget | EventTask | see below Event Target for more details |
| HTMLElement on properties | EventTask | see below on properties for more details |
| XMLHttpRequest.send/abort | MacroTask | |
| XMLHttpRequest on properties | EventTask | |
| IDBIndex on properties | EventTask | |
| IDBRequest on properties | EventTask | |
| IDBOpenDBRequest on properties | EventTask | |
| IDBDatabaseRequest on properties | EventTask | |
| IDBTransaction on properties | EventTask | |
| IDBCursor on properties | EventTask | |
| WebSocket on properties | EventTask | |
| MutationObserver | wrap | |
| WebkitMutationObserver | wrap | |
| FileReader | wrap | |
| registerElement | wrap | |

EventTarget

- For browsers supporting EventTarget, Zone.js just patches EventTarget, so everything that inherits
from EventTarget will also be patched.
- For browsers that do not support EventTarget, Zone.js will patch the following APIs in the IDL
 that inherit from EventTarget
 
 |||||
 |---|---|---|---|
 |ApplicationCache|EventSource|FileReader|InputMethodContext|
 |MediaController|MessagePort|Node|Performance|
 |SVGElementInstance|SharedWorker|TextTrack|TextTrackCue|
 |TextTrackList|WebKitNamedFlow|Window|Worker|
 |WorkerGlobalScope|XMLHttpRequest|XMLHttpRequestEventTarget|XMLHttpRequestUpload|
 |IDBRequest|IDBOpenDBRequest|IDBDatabase|IDBTransaction|
 |IDBCursor|DBIndex|WebSocket|

The following 'on' properties, such as onclick, onreadystatechange, are patched in Zone.js as EventTasks

 |||||
 |---|---|---|---|
 |copy|cut|paste|abort|
 |blur|focus|canplay|canplaythrough|
 |change|click|contextmenu|dblclick|
 |drag|dragend|dragenter|dragleave|
 |dragover|dragstart|drop|durationchange|
 |emptied|ended|input|invalid|
 |keydown|keypress|keyup|load|
 |loadeddata|loadedmetadata|loadstart|message|
 |mousedown|mouseenter|mouseleave|mousemove|
 |mouseout|mouseover|mouseup|pause|
 |play|playing|progress|ratechange|
 |reset|scroll|seeked|seeking|
 |select|show|stalled|submit|
 |suspend|timeupdate|volumechange|waiting|
 |mozfullscreenchange|mozfullscreenerror|mozpointerlockchange|mozpointerlockerror|
 |error|webglcontextrestored|webglcontextlost|webglcontextcreationerror|

## NodeJS

| API | Patch Mechanism | Others |
| --- | --- | --- |
| setTimeout/clearTimeout | MacroTask | app can get handlerId, interval, args, isPeriodic(false) through task.data |
| setImmediate/clearImmediate | MacroTask | same with setTimeout |
| setInterval/clearInterval | MacroTask | isPeriodic is true, so setInterval will not trigger onHasTask callback | 
| process.nextTick | Microtask | isPeriodic is true, so setInterval will not trigger onHasTask callback | 
| Promise | MicroTask |  |
| EventEmitter | EventTask | All APIs inherit EventEmitter are patched as EventTask  |
| crypto | MacroTask |  |
| fs | MacroTask | all async methods are patched |

EventEmitter, addEventListener, prependEventListener and 'on' will be patched once as EventTasks, and removeEventListener and
removeAllListeners will remove those EventTasks

## Electron 

Zone.js does not patch the Electron API, although in Electron both browser APIs and node APIs are patched, so 
if you want to include Zone.js in Electron, please use dist/zone-mix.js

## ZoneAwareError

ZoneAwareError replaces global Error, and adds zone information to stack trace.
ZoneAwareError also handles 'this' issue.
This type of issue would happen when creating an error without `new`: `this` would be `undefined` in strict mode, and `global` in
non-strict mode. It could cause some very difficult to detect issues.

```javascript
  const error = Error(); 
```

ZoneAwareError makes sure that `this` is ZoneAwareError even without new.

## ZoneAwarePromise

ZoneAwarePromise wraps the global Promise and makes it run in zones as a MicroTask.
It also passes promise A+ tests.

## BlackListEvents

Sometimes we don't want some `event` to be patched by `zone.js`, we can blacklist events
by following settings.

```javascript
    // disable on properties
    var targets = [window, Document, HTMLBodyElement, HTMLElement];
    __Zone_ignore_on_properties = [];
    targets.forEach(function (target) {
      __Zone_ignore_on_properties.push({
        target: target,
        ignoreProperties: ['scroll']
      });
    });

    // disable addEventListener
    global['__zone_symbol__BLACK_LISTED_EVENTS'] = ['scroll'];
```