javascript – What Typescript type is Angular2 event-ThrowExceptions

Exception or error:

If I have the following button in an html file

<button (click)="doSomething('testing', $event)">Do something</button>

Also, in the corresponding component, I have this function

doSomething(testString: string, event){
    event.stopPropagation();
    console.log(testString + ': I am doing something');
}

Is there a proper type that should be assigned to the $event input?
The event parameter itself is an object, BUT if I assign it to a type object, I get an error

Property ‘stopPropogation’ does not exist on type object

So, what does Typescript consider the $event input?

How to solve:

As suggested by @AlexJ

The event you passed through $event is a DOM event, therefore you can use the EventName as the type.

In your case this event is a MouseEvent, and the docs says, quoting

The MouseEvent interface represents events that occur due to the user interacting with a pointing device (such as a mouse). Common events using this interface include click, dblclick, mouseup, mousedown.

In all those cases you’ll get a MouseEvent.

Another example : if you have this code

<input type="text" (blur)="event($event)"

When the event triggers you’ll get a FocusEvent.

So you can do it really simple, console log the event and you’ll see a message similar to this one that’ll we have the event name

FocusEvent {isTrusted: true, relatedTarget: null, view: Window, detail: 0, which: 0…}

You can always visit the docs for a list of existing Events.

Edit

You can also check for TypeScript dom.generated.d.ts with all the typings ported. In your case stopPropagation() is part of Event, extended by MouseEvent.

###

Some commonly used events and their related names (MouseEvent, FocusEvent, TouchEvent, DragEvent, KeyboardEvent):

| MouseEvent | FocusEvent |  TouchEvent | DragEvent | KeyboardEvent |
|:----------:|:----------:|:-----------:|:---------:|:-------------:|
|    click   |    focus   |  touchstart |    drag   |    keypress   |
|   mouseup  |    blur    |  touchmove  |    drop   |     keyup     |
| mouseleave |   focusin  | touchcancel |  dragend  |    keydown    |
|  mouseover |  focusout  |   touchend  |  dragover |               |

The generic Event is associated to:

  • close
  • change
  • invalid
  • play
  • reset
  • scroll
  • select
  • submit
  • toggle
  • waiting

If you dig in Typescript’s repository, dom.generated.d.ts provides a global events interface (credit goes to Eric’s answer) where you may find all the event handlers mappings at line 5725:

interface GlobalEventHandlersEventMap {
  "abort": UIEvent;
  "animationcancel": AnimationEvent;
  "animationend": AnimationEvent;
  "animationiteration": AnimationEvent;
  "animationstart": AnimationEvent;
  "auxclick": MouseEvent;
  "blur": FocusEvent;
  "cancel": Event;
  "canplay": Event;
  "canplaythrough": Event;
  "change": Event;
  "click": MouseEvent;
  "close": Event;
  "contextmenu": MouseEvent;
  "cuechange": Event;
  "dblclick": MouseEvent;
  "drag": DragEvent;
  "dragend": DragEvent;
  "dragenter": DragEvent;
  "dragexit": Event;
  "dragleave": DragEvent;
  "dragover": DragEvent;
  "dragstart": DragEvent;
  "drop": DragEvent;
  "durationchange": Event;
  "emptied": Event;
  "ended": Event;
  "error": ErrorEvent;
  "focus": FocusEvent;
  "focusin": FocusEvent;
  "focusout": FocusEvent;
  "gotpointercapture": PointerEvent;
  "input": Event;
  "invalid": Event;
  "keydown": KeyboardEvent;
  "keypress": KeyboardEvent;
  "keyup": KeyboardEvent;
  "load": Event;
  "loadeddata": Event;
  "loadedmetadata": Event;
  "loadend": ProgressEvent;
  "loadstart": Event;
  "lostpointercapture": PointerEvent;
  "mousedown": MouseEvent;
  "mouseenter": MouseEvent;
  "mouseleave": MouseEvent;
  "mousemove": MouseEvent;
  "mouseout": MouseEvent;
  "mouseover": MouseEvent;
  "mouseup": MouseEvent;
  "pause": Event;
  "play": Event;
  "playing": Event;
  "pointercancel": PointerEvent;
  "pointerdown": PointerEvent;
  "pointerenter": PointerEvent;
  "pointerleave": PointerEvent;
  "pointermove": PointerEvent;
  "pointerout": PointerEvent;
  "pointerover": PointerEvent;
  "pointerup": PointerEvent;
  "progress": ProgressEvent;
  "ratechange": Event;
  "reset": Event;
  "resize": UIEvent;
  "scroll": Event;
  "securitypolicyviolation": SecurityPolicyViolationEvent;
  "seeked": Event;
  "seeking": Event;
  "select": Event;
  "selectionchange": Event;
  "selectstart": Event;
  "stalled": Event;
  "submit": Event;
  "suspend": Event;
  "timeupdate": Event;
  "toggle": Event;
  "touchcancel": TouchEvent;
  "touchend": TouchEvent;
  "touchmove": TouchEvent;
  "touchstart": TouchEvent;
  "transitioncancel": TransitionEvent;
  "transitionend": TransitionEvent;
  "transitionrun": TransitionEvent;
  "transitionstart": TransitionEvent;
  "volumechange": Event;
  "waiting": Event;
  "wheel": WheelEvent;
}

###

According to official event is of type Object, also in my case when i typecaste event to the Object it does’t throw any error, but after reading documentation of angular2 found event is of type EventEmitter so you can type caste your event into EventEmitter

see here is plunkr for the same http://plnkr.co/edit/8HRA3bM0NxXrzBAjWYXc?p=preview

for more info refer here https://angular.io/docs/ts/latest/guide/template-syntax.html#!#event-binding

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