Object.entries()
方法返回一个给定对象自身可枚举属性的键值对数组,其排列与使用
for...in
循环遍历该对象时返回的顺序一致(区别在于 for-in 循环还会枚举原型链中的属性)。
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
语法
Object.entries(obj)
参数
-
obj
- 可以返回其可枚举属性的键值对的对象。
返回值
- 给定对象自身可枚举属性的键值对数组。
描述
Object.entries()
返回一个数组,其元素是与直接在object
上找到的可枚举属性键值对相对应的数组。属性的顺序与通过手动循环对象的属性值所给出的顺序相同。
示例
const obj = { foo: 'bar', baz: 42 }; console.log(Object.entries(obj)); // [ ['foo', 'bar'], ['baz', 42] ] // array like object const obj = { 0: 'a', 1: 'b', 2: 'c' }; console.log(Object.entries(obj)); // [ ['0', 'a'], ['1', 'b'], ['2', 'c'] ] // array like object with random key ordering const anObj = { 100: 'a', 2: 'b', 7: 'c' }; console.log(Object.entries(anObj)); // [ ['2', 'b'], ['7', 'c'], ['100', 'a'] ] // getFoo is property which isn't enumerable const myObj = Object.create({}, { getFoo: { value() { return this.foo; } } }); myObj.foo = 'bar'; console.log(Object.entries(myObj)); // [ ['foo', 'bar'] ] // non-object argument will be coerced to an object console.log(Object.entries('foo')); // [ ['0', 'f'], ['1', 'o'], ['2', 'o'] ] // iterate through key-value gracefully const obj = { a: 5, b: 7, c: 9 }; for (const [key, value] of Object.entries(obj)) { console.log(`${key} ${value}`); // "a 5", "b 7", "c 9" } // Or, using array extras Object.entries(obj).forEach(([key, value]) => { console.log(`${key} ${value}`); // "a 5", "b 7", "c 9" });
将Object
转换为Map
Map
:
var obj = { foo: "bar", baz: 42 }; var map = new Map(Object.entries(obj)); console.log(map); // Map { foo: "bar", baz: 42 }
Polyfill
要在较旧环境中添加兼容的Object.entries
支持,你可以在 tc39/proposal-object-values-entries 中找到Object.entries的示例(如果你不需要任何对IE的支持),在 es-shims/Object.entries 资料库中的一个polyfill,或者你可以使用下面列出的简易 polyfill。
if (!Object.entries) Object.entries = function( obj ){ var ownProps = Object.keys( obj ), i = ownProps.length, resArray = new Array(i); // preallocate the Array while (i--) resArray[i] = [ownProps[i], obj[ownProps[i]]]; return resArray; };
对于上述 polyfill 代码片段,如果你需要 IE9 以下的支持,那么你还需要一个 Object.keys polyfill(如 Object.keys
页面上的)。
规范
Specification | Status | Comment |
---|---|---|
ECMAScript Latest Draft (ECMA-262) Object.entries |
Draft | Initial definition. |
ECMAScript 2017 (ECMA-262) Object.entries |
Standard |
浏览器兼容
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out
https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
entries |
Chrome Full support 54 | Edge Full support 14 | Firefox Full support 47 | IE No support No | Opera Full support 41 | Safari Full support 10.1 | WebView Android Full support 54 | Chrome Android Full support 54 | Firefox Android Full support 47 | Opera Android Full support 41 | Safari iOS Full support 10.3 | Samsung Internet Android Full support 6.0 | nodejs Full support 7.0.0
|
Legend
- Full support
- Full support
- No support
- No support
- User must explicitly enable this feature.
- User must explicitly enable this feature.