commit
e60f94cdae
@ -0,0 +1,70 @@ |
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if (!('EventEmitter' in window)) { |
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window.EventEmitter = class EventEmitter { |
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constructor () { |
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this._listeners = {} |
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} |
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|
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/** |
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* Bind an event listener to an event |
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* @param {string} event - the event name |
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* @param {Function} listener - the event listener |
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*/ |
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on (event, listener) { |
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if (!this._listeners[event]) this._listeners[event] = [] |
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this._listeners[event].push({ listener }) |
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} |
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|
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/** |
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* Bind an event listener to be run only once the next time the event fires |
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* @param {string} event - the event name |
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* @param {Function} listener - the event listener |
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*/ |
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once (event, listener) { |
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if (!this._listeners[event]) this._listeners[event] = [] |
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this._listeners[event].push({ listener, once: true }) |
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} |
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|
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/** |
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* Remove an event listener |
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* @param {string} event - the event name |
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* @param {Function} listener - the event listener |
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*/ |
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off (event, listener) { |
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let listeners = this._listeners[event] |
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if (listeners) { |
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for (let i in listeners) { |
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if (listeners[i].listener === listener) { |
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listeners.splice(i, 1) |
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break |
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} |
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} |
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} |
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} |
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|
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/** |
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* Emits an event |
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* @param {string} event - the event name |
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* @param {...any} args - arguments passed to all listeners |
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*/ |
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emit (event, ...args) { |
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let listeners = this._listeners[event] |
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if (listeners) { |
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let remove = [] |
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for (let listener of listeners) { |
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try { |
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listener.listener(...args) |
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if (listener.once) remove.push(listener) |
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} catch (err) { |
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console.error(err) |
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} |
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} |
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|
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// this needs to be done in this roundabout way because for loops
|
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// do not like arrays with changing lengths
|
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for (let listener of remove) { |
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listeners.splice(listeners.indexOf(listener), 1) |
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} |
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} |
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} |
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} |
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} |
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