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December 31, 2015 18:38
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A quick promise implementation in JS to showcase how simple it is to implement a promise. Don't use in a production app!
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| function promise() { | |
| var listeners = [], | |
| resolved = false, | |
| data; | |
| return { | |
| isResolved: function() { | |
| return resolved; | |
| }, | |
| whenDone: function(cb) { | |
| if(resolved) | |
| cb(data); | |
| else | |
| listeners.push(cb); | |
| }, | |
| resolve: function(d) { | |
| resolved = true; | |
| data = d; | |
| listeners.forEach(function(cb) { | |
| cb(data); | |
| }); | |
| listeners = []; | |
| } | |
| }; | |
| } | |
| // Sample usage | |
| var p = promise(); | |
| //... | |
| p.whenDone(function(data) { | |
| // do something with the data | |
| }); | |
| // ... | |
| p.resolve(42); |
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