同时不重新构造并分配给新的变量 [英] Destructure and assign to new variable at the same time not working

问题描述

  let {x} = a = {x：'cool'}; 
 console.log（a，x）; 
  

其中输出：

 Firefox 
 //引用错误：a没有定义 - 在Chrome，babel-node 
 中的对象{x：cool}酷 - 

为什么有区别，什么是正确的行为？

更新：

这可能是更通用的用例。虽然这适用于所有环境：

  var a = b = {x：'cool'}; 
  

此语句在chrome / babel-node中不起作用：

  var {x} = a = {x：'cool'}; // SyntaxError：Unexpected token {
  

使用时也有不同的错误信息var 而不是 let 。

解决方案

在你的代码中，没有定义 a 。 let a = b = c 不定义 b 。你需要说

  let a = {x：1}，{x} = a; 
  

Firefox不支持 let 我想知道你的例子如何在那里工作。请参阅 https://kangax.github.io/compat-table/es6/ 。

I am trying to destructure object and assign it to new variable at the same time:

let {x} = a = {x: 'cool'};
console.log(a, x);

which outputs:

//Object { x: "cool" } cool - in Firefox
//ReferenceError: a is not defined - in Chrome, babel-node

Why is there difference and what is the correct behavior?

UPDATE:

This is maybe more generic use case. While this works in all environments:

var a = b = {x: 'cool'};

this statement is not working in chrome/babel-node:

var {x} = a = {x: 'cool'}; //SyntaxError: Unexpected token {

There is also different error message when using var instead of let.

解决方案

In your code, a is not defined. let a = b = c does not define b. You need to say

let a = {x: 1}, {x} = a;

Firefox doesn't support let, so I'm wondering how your example worked there at all. See https://kangax.github.io/compat-table/es6/.

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