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Fun with Javascript Prototypes
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| Function.prototype.if = function (conditional) { | |
| return input => conditional(input) ? this(input) : input; | |
| } | |
| let double = x => x * 2; | |
| let positive = x => x > 0; | |
| [2, -4, 6, -8].map(double.if(positive)); | |
| // [4, -4, 12, -8] | |
| Function.prototype.patch = function (func) { | |
| return (...args) => func.apply(this, args); | |
| } | |
| double = double.patch(function (input) { | |
| console.log(`about to double ${input}`); | |
| const result = this(input); | |
| console.log('we did it'); | |
| return result; | |
| }); | |
| [2, -4, 6, -8].map(double.if(positive)); | |
| // about to double 2 | |
| // we did it | |
| // about to double 6 | |
| // we did it | |
| // [4, -4, 12, -8] |
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