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denoland-deno/js/event_target.ts

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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
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import * as domTypes from "./dom_types";
/* TODO: This is an incomplete implementation to provide functionality
* for Event. A proper spec is still required for a proper Web API.
*/
export class EventTarget implements domTypes.EventTarget {
public listeners: {
[type in string]: domTypes.EventListenerOrEventListenerObject[]
} = {};
public addEventListener(
type: string,
listener: domTypes.EventListenerOrEventListenerObject | null,
_options?: boolean | domTypes.AddEventListenerOptions
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): void {
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if (!this.listeners.hasOwnProperty(type)) {
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this.listeners[type] = [];
}
if (listener !== null) {
this.listeners[type].push(listener);
}
}
public removeEventListener(
type: string,
callback: domTypes.EventListenerOrEventListenerObject | null,
_options?: domTypes.EventListenerOptions | boolean
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): void {
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if (this.listeners.hasOwnProperty(type) && callback !== null) {
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this.listeners[type] = this.listeners[type].filter(
listener => listener !== callback
);
}
}
public dispatchEvent(event: domTypes.Event): boolean {
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if (!this.listeners.hasOwnProperty(event.type)) {
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return true;
}
const stack = this.listeners[event.type].slice();
for (const stackElement of stack) {
if ((stackElement as domTypes.EventListenerObject).handleEvent) {
(stackElement as domTypes.EventListenerObject).handleEvent(event);
} else {
(stackElement as domTypes.EventListener).call(this, event);
}
}
return !event.defaultPrevented;
}
}