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Javascript prototype in a nutshell
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| var assert = require('assert') | |
| var util = require('util') | |
| function test (inherits) { | |
| function Fruit () { | |
| } | |
| Fruit.prototype.round = false | |
| Fruit.prototype.sweet = true | |
| Fruit.prototype.eat = function () {} | |
| function Apple () { | |
| } | |
| inherits(Apple, Fruit) | |
| Apple.prototype.round = true | |
| var fruit = new Fruit() | |
| var apple = new Apple() | |
| // *class*, *instance* and *prototype* | |
| assert.equal(fruit.constructor, Fruit) | |
| assert.equal(fruit.constructor.prototype, Fruit.prototype) | |
| assert.equal(fruit.constructor.prototype.constructor, Fruit) | |
| assert.equal(Object.getPrototypeOf(fruit), Fruit.prototype) | |
| // *prototype chain* | |
| assert.equal(Object.getPrototypeOf(apple), Apple.prototype) | |
| assert.equal(Object.getPrototypeOf(Object.getPrototypeOf(apple)), Fruit.prototype) | |
| assert.equal(Object.getPrototypeOf(Object.getPrototypeOf(Object.getPrototypeOf(apple))), Object.prototype) | |
| assert.equal(Object.getPrototypeOf(Object.getPrototypeOf(Object.getPrototypeOf(Object.getPrototypeOf(apple)))), null) | |
| // *property* | |
| assert.equal(fruit.round, false) | |
| assert.equal(fruit.sweet, true) | |
| assert.equal(apple.round, true) | |
| assert.equal(apple.sweet, true) | |
| Apple.prototype = {} | |
| assert.equal(apple.round, true) | |
| assert.equal(apple.sweet, true) | |
| // magic *__proto__* property | |
| assert.equal(Object.getPrototypeOf(fruit), fruit.__proto__) | |
| apple.__proto__ = {} | |
| assert.equal(apple.round, undefined) | |
| assert.equal(apple.sweet, undefined) | |
| } | |
| var inherits0 = util.inherits | |
| function inherits1 (constructor, superConstructor) { | |
| // leverage *new* keyword to setup prototype | |
| var EmptyFunc = function () {} | |
| EmptyFunc.prototype = superConstructor.prototype | |
| var proto = new EmptyFunc() | |
| proto.constructor = constructor | |
| constructor.prototype = proto | |
| } | |
| function inherits2 (constructor, superConstructor) { | |
| var proto = Object.create(superConstructor.prototype) | |
| proto.constructor = constructor | |
| constructor.prototype = proto | |
| } | |
| function inherits3 (constructor, superConstructor) { | |
| var proto = {} | |
| Object.setPrototypeOf(proto, superConstructor.prototype) | |
| proto.constructor = constructor | |
| constructor.prototype = proto | |
| } | |
| function inherits4 (constructor, superConstructor) { | |
| var proto = {} | |
| proto.__proto__ = superConstructor.prototype | |
| proto.constructor = constructor | |
| constructor.prototype = proto | |
| } | |
| test(inherits0) | |
| test(inherits1) | |
| test(inherits2) | |
| test(inherits3) | |
| test(inherits4) |
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