From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:40:17 -0500 Subject: initial commit --- .../global_objects/object/entries/index.html | 134 +++++++++++++++++++++ 1 file changed, 134 insertions(+) create mode 100644 files/zh-cn/web/javascript/reference/global_objects/object/entries/index.html (limited to 'files/zh-cn/web/javascript/reference/global_objects/object/entries') diff --git a/files/zh-cn/web/javascript/reference/global_objects/object/entries/index.html b/files/zh-cn/web/javascript/reference/global_objects/object/entries/index.html new file mode 100644 index 0000000000..6e704940a5 --- /dev/null +++ b/files/zh-cn/web/javascript/reference/global_objects/object/entries/index.html @@ -0,0 +1,134 @@ +--- +title: Object.entries() +slug: Web/JavaScript/Reference/Global_Objects/Object/entries +tags: + - JavaScript + - Method + - Object + - Reference +translation_of: Web/JavaScript/Reference/Global_Objects/Object/entries +--- +
{{JSRef}}
+ +

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 {{jsxref("Statements/for...in", "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）。

+ +
{{EmbedInteractiveExample("pages/js/object-entries.html", "taller")}}
+ + + +

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

+ +

{{jsxref("Map", "new Map()")}} 构造函数接受一个可迭代的entries。借助Object.entries方法你可以很容易的将{{jsxref("Object")}}转换为{{jsxref("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 {{jsxref("Object.keys")}}页面上的）。

+ +

规范

+ + + + + + + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('ESDraft', '#sec-object.entries', 'Object.entries')}}{{Spec2('ESDraft')}}Initial definition.
{{SpecName('ES8', '#sec-object.entries', 'Object.entries')}}{{Spec2('ES8')}}
+ +

浏览器兼容

+ + + +

{{Compat("javascript.builtins.Object.entries")}}

+ +

相关链接

+ + -- cgit v1.2.3-54-g00ecf