1 | /**
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2 | * Event emitter class
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3 | */
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4 | export class Emitter {
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5 | /**
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6 | * Creates an instance of Emitter.
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7 | */
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8 | constructor() {
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9 | /**
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10 | * Events object
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11 | * @type {Object}
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12 | */
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13 | this.events = {};
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14 | }
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15 |
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16 | /**
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17 | * Subscribe to an event
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18 | * @param {Array} evts Collection of event names
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19 | * @param {Function} fn Function invoked when event is emitted
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20 | */
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21 | on(evts, fn) {
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22 | evts.forEach((evt) => {
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23 | this.events[evt] = this.events[evt] || [];
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24 | this.events[evt].push(fn);
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25 | });
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26 | }
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27 |
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28 | /**
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29 | * Unsubscribe to an event
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30 | * @param {Array} evts Collection of event names
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31 | * @param {Function} fn Function invoked when event is emitted
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32 | */
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33 | off(evts, fn) {
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34 | evts.forEach((evt) => {
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35 | if (evt in this.events) {
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36 | this.events[evt].splice(this.events[evt].indexOf(fn), 1);
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37 | }
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38 | });
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39 | }
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40 |
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41 | /**
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42 | * Emit an event
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43 | * @param {String} evt Event name followed by any other argument passed to
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44 | * the invoked function
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45 | */
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46 | emit(evt /*, args...*/) {
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47 | if (evt in this.events) {
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48 | for (let i = 0; i < this.events[evt].length; i++) {
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49 | this.events[evt][i].apply(this, [].slice.call(arguments, 1));
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50 | }
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51 | }
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52 | }
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53 | }
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