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39 lines
1016 B
39 lines
1016 B
2 years ago
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= Object 方法
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== Object.defineProperty
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该方法会直接在一个对象上定义一个新属性，或者修改一个对象的现有属性，并返回此对象。
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[source,javascript]
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----
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const object1 = {};
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Object.defineProperty(object1, 'property1', {
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value: 42,
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writable: false
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});
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object1.property1 = 77;
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// throws an error in strict mode
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console.log(object1.property1);
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// expected output: 42
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----
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NOTE: 应当直接在 Object 构造器对象上调用此方法，而不是在任意一个 Object 类型的实例上调用。
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== Object.prototype.hasOwnProperty
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该方法会返回一个布尔值，指示对象自身属性中是否具有指定的属性（也就是，是否有指定的键）。
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[source,javascript]
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----
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const object1 = {};
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object1.property1 = 42;
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console.log(object1.hasOwnProperty('property1'));
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// expected output: true
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console.log(object1.hasOwnProperty('toString'));
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// expected output: false
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console.log(object1.hasOwnProperty('hasOwnProperty'));
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// expected output: false
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----
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