赋值左侧的 Javascript 对象括号表示法 ({ Navigation } =) [英] Javascript object bracket notation ({ Navigation } =) on left side of assign

问题描述

我以前没有见过这种语法，我想知道它是怎么回事.

I haven't seen this syntax before and am wondering what it's all about.

var { Navigation } = require('react-router');

左边的括号抛出语法错误:

The brackets on the left are throwing a syntax error:

意外的令牌{

我不确定 webpack 配置的哪一部分正在转换或语法的目的是什么.是和谐的东西吗?有人可以启发我吗?

I'm not sure what part of the webpack config is transforming or what the purpose of the syntax is. Is it a Harmony thing? Can someone enlighten me?

推荐答案

叫做 解构赋值，它是ES2015标准的一部分.

It's called destructuring assignment and it's part of the ES2015 standard.

解构赋值语法是一个 JavaScript 表达式可以使用 a 从数组或对象中提取数据反映数组和对象字面量构造的语法.

The destructuring assignment syntax is a JavaScript expression that makes it possible to extract data from arrays or objects using a syntax that mirrors the construction of array and object literals.

来源: 解构赋值参考在 MDN 上

对象解构

 var o = {p: 42, q: true};
 var {p, q} = o;

 console.log(p); // 42
 console.log(q); // true 

 // Assign new variable names
 var {p: foo, q: bar} = o;

 console.log(foo); // 42
 console.log(bar); // true

数组解构

var foo = ["one", "two", "three"];

// without destructuring
var one   = foo[0];
var two   = foo[1];
var three = foo[2];

// with destructuring
var [one, two, three] = foo;

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