1 | # event-emitter
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2 | ## Environment agnostic event emitter
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3 |
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4 | ### Installation
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5 |
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6 | $ npm install event-emitter
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7 |
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8 | To port it to Browser or any other (non CJS) environment, use your favorite CJS bundler. No favorite yet? Try: [Browserify](http://browserify.org/), [Webmake](https://github.com/medikoo/modules-webmake) or [Webpack](http://webpack.github.io/)
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9 |
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10 | ### Usage
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11 |
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12 | ```javascript
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13 | var ee = require('event-emitter');
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14 |
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15 | var MyClass = function () { /* .. */ };
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16 | ee(MyClass.prototype); // All instances of MyClass will expose event-emitter interface
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17 |
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18 | var emitter = new MyClass(), listener;
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19 |
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20 | emitter.on('test', listener = function (args) {
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21 | // … react to 'test' event
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22 | });
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23 |
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24 | emitter.once('test', function (args) {
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25 | // … react to first 'test' event (invoked only once!)
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26 | });
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27 |
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28 | emitter.emit('test', arg1, arg2/*…args*/); // Two above listeners invoked
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29 | emitter.emit('test', arg1, arg2/*…args*/); // Only first listener invoked
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30 |
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31 | emitter.off('test', listener); // Removed first listener
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32 | emitter.emit('test', arg1, arg2/*…args*/); // No listeners invoked
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33 | ```
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34 | ### Additional utilities
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35 |
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36 | #### allOff(obj) _(event-emitter/all-off)_
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37 |
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38 | Removes all listeners from given event emitter object
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39 |
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40 | #### hasListeners(obj[, name]) _(event-emitter/has-listeners)_
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41 |
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42 | Whether object has some listeners attached to the object.
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43 | When `name` is provided, it checks listeners for specific event name
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44 |
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45 | ```javascript
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46 | var emitter = ee();
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47 | var hasListeners = require('event-emitter/has-listeners');
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48 | var listener = function () {};
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49 |
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50 | hasListeners(emitter); // false
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51 |
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52 | emitter.on('foo', listener);
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53 | hasListeners(emitter); // true
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54 | hasListeners(emitter, 'foo'); // true
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55 | hasListeners(emitter, 'bar'); // false
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56 |
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57 | emitter.off('foo', listener);
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58 | hasListeners(emitter, 'foo'); // false
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59 | ```
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60 |
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61 | #### pipe(source, target[, emitMethodName]) _(event-emitter/pipe)_
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62 |
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63 | Pipes all events from _source_ emitter onto _target_ emitter (all events from _source_ emitter will be emitted also on _target_ emitter, but not other way).
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64 | Returns _pipe_ object which exposes `pipe.close` function. Invoke it to close configured _pipe_.
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65 | It works internally by redefinition of `emit` method, if in your interface this method is referenced differently, provide its name (or symbol) with third argument.
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66 |
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67 | #### unify(emitter1, emitter2) _(event-emitter/unify)_
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68 |
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69 | Unifies event handling for two objects. Events emitted on _emitter1_ would be also emitted on _emitter2_, and other way back.
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70 | Non reversible.
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71 |
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72 | ```javascript
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73 | var eeUnify = require('event-emitter/unify');
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74 |
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75 | var emitter1 = ee(), listener1, listener3;
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76 | var emitter2 = ee(), listener2, listener4;
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77 |
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78 | emitter1.on('test', listener1 = function () { });
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79 | emitter2.on('test', listener2 = function () { });
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80 |
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81 | emitter1.emit('test'); // Invoked listener1
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82 | emitter2.emit('test'); // Invoked listener2
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83 |
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84 | var unify = eeUnify(emitter1, emitter2);
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85 |
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86 | emitter1.emit('test'); // Invoked listener1 and listener2
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87 | emitter2.emit('test'); // Invoked listener1 and listener2
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88 |
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89 | emitter1.on('test', listener3 = function () { });
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90 | emitter2.on('test', listener4 = function () { });
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91 |
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92 | emitter1.emit('test'); // Invoked listener1, listener2, listener3 and listener4
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93 | emitter2.emit('test'); // Invoked listener1, listener2, listener3 and listener4
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94 | ```
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95 |
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96 | ### Tests [![Build Status](https://travis-ci.org/medikoo/event-emitter.png)](https://travis-ci.org/medikoo/event-emitter)
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97 |
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98 | $ npm test
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