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Lazy object properties
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| ///////////////////////////////////////////////// | |
| //// Lazy object properties | |
| ///////////////////////////////////////////////// | |
| // Sets a property that computes its value on first access | |
| // (see a test below for usage example) | |
| function lazy(obj, prop, fn){ | |
| if(typeof prop === 'string') set(prop, fn) | |
| else Object.keys(prop).forEach(function(k){ set(k, prop[k]) }) | |
| function set(name, fn){ | |
| // Set getter | |
| Object.defineProperty(obj, name, { | |
| get: function(){ | |
| // Calculate value on first access | |
| var value = fn(name, obj) | |
| // Set value | |
| Object.defineProperty(obj, name, { | |
| value: value, | |
| enumerable: true, | |
| configurable: true, | |
| writable: true | |
| }) | |
| return value | |
| }, | |
| enumerable: true, | |
| configurable: true | |
| }) | |
| } | |
| return obj | |
| } | |
| /* | |
| (function test(){ | |
| var obj = lazy({}, {test: function(){ return Math.random() }}) | |
| // Test | |
| var calculated = obj.test | |
| var predefined = obj.test | |
| console.log(calculated === predefined, calculated, predefined) | |
| })() | |
| */ |
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