javascript - es6 object syntax

Question

What does it mean

var { auth = true } = meta

It feels like {} is an object, but the format inside is not quite right. Shouldn’t it be { auth: true }, and then assign a value meta value? Don’t know what it means

Answer 1

Here is object destructuring in ES6

//对象的解构也可以指定默认值。
var {x = 3} = {};
x // 3

var {x, y = 5} = {x: 1};
x // 1
y // 5

var {x:y = 3} = {};
y // 3

var {x:y = 3} = {x: 5};
y // 5

var { message: msg = 'Something went wrong' } = {};
msg // "Something went wrong"

For this kind of problem, I hope you can check it later through the babeljs.io official online compiler

// 上面的代码，可以这样理解
var auth = meta.auth === undefined ? true : meta.auth;

Answer 2

Destructuring assignment.

New features in es6.

Answer 3

This outside is destructuring assignment

This is the default value

Answer 4

var meta = {
    auth: 33   // 把这个去掉你看看输出的值是什么？
};

// {auth = true}  是设置默认值。
var { auth = true } = meta;  // meta 是一个对象， 如果auth没有， auth 等于 true

console.log(auth);

Answer 5

If written in es5, it is like this:

var auth = (typeof meta.auth!=='undefined')? meta.auth: true;

Answer 6

Destructuring assignment in ES6

{ auth = true } It is equivalent to assigning a default value to auth. If the value of the auth attribute in the meta object is undefined, the default value true will be assigned to the variable auth