65 lines
1.9 KiB
Markdown
65 lines
1.9 KiB
Markdown
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---
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title: Object Keys
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localeTitle: 对象键
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---
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`Object.keys()`方法返回给定对象自己的可枚举属性的数组，其顺序与`for...in`循环提供的顺序相同（不同之处在于`for-in`循环枚举原型链中的属性为好）。
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## 句法
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```
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Object.keys(obj)
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```
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### 参数
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**OBJ**
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要返回其可枚举自身属性的对象。
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[MDN链接](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys) | [MSDN链接](https://msdn.microsoft.com/en-us/LIBRary/ff688127%28v=vs.94%29.aspx)
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## 描述
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`Object.keys()`返回一个数组，其元素是与直接在对象上找到的可枚举属性相对应的字符串。属性的顺序与通过手动循环对象的属性给出的顺序相同。
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## 例子
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```
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var arr = ['a', 'b', 'c'];
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console.log(Object.keys(arr)); // console: ['0', '1', '2']
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// array like object
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var obj = { 0: 'a', 1: 'b', 2: 'c' };
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console.log(Object.keys(obj)); // console: ['0', '1', '2']
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// array like object with random key ordering
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var an_obj = { 100: 'a', 2: 'b', 7: 'c' };
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console.log(Object.keys(an_obj)); // console: ['2', '7', '100']
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// getFoo is property which isn't enumerable
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var my_obj = Object.create({}, { getFoo: { value: function() { return this.foo; } } });
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my_obj.foo = 1;
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console.log(Object.keys(my_obj)); // console: ['foo']
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// Create a constructor function.
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function Pasta(grain, width, shape) {
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this.grain = grain;
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this.width = width;
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this.shape = shape;
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// Define a method.
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this.toString = function () {
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return (this.grain + ", " + this.width + ", " + this.shape);
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}
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}
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// Create an object.
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var spaghetti = new Pasta("wheat", 0.2, "circle");
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// Put the enumerable properties and methods of the object in an array.
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var arr = Object.keys(spaghetti);
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document.write (arr);
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// Output:
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// grain,width,shape,toString
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```
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