当前位置:首页 >> 网络编程

基于ES6作用域和解构赋值详解

ES6 强制开启严格模式

作用域

"htmlcode">

// const声明的k指向一个对象,k本身不可变,但对象可变

function test() {
 const k={
  a:1
 }
 k.b=3;
 
 console.log(k);
}

test()解构赋值

{
 let a, b, 3, rest;
 [a, b, c=3]=[1, 2];

 console.log(a, b);
}
//output: 1 2 3

{
 let a, b, 3, rest;
 [a, b, c]=[1, 2];

 console.log(a, b);
}
//output: 1 2 undefined

{
 let a, b, rest;
 [a, b, ...rest] = [1, 2, 3, 4, 5, 6];
 console.log(a, b, rest);
}
//output:1 2 [3, 4, 5, 6]

{
 let a, b;
 ({a, b} = {a:1, b:2})

 console.log(a ,b);
}
//output: 1 2

使用场景

变量交换

{
 let a = 1;
 let b = 2;
 [a, b] = [b, a];
 console.log(a, b);
}

获取多个函数值

{
 function f(){
  return [1, 2]
 }
 let a, b;
 [a, b] = f();
 console.log(a, b);
}

获取多个函数返回值

{
 function f(){
  return [1, 2, 3, 4, 5]
 }
 let a, b, c;
 [a,,,b] = f();
 console.log(a, b);
}
//output: 1 4

{
 function f(){
  return [1, 2, 3, 4, 5]
 }
 let a, b, c;
 [a, ...b] = f();
 console.log(a, b);
}
//output: 1 [2, 3, 4, 5]

对象解构赋值

{
 let o={p:42, q:true};
 let {p, q, c=5} = o;

 console.log(p ,q);
}
//output: 42 true 5

获取json值

{
 let metaData={
  title: 'abc',
  test: [{
   title: 'test',
   desc: 'description'
  }]
 }
 let {title:esTitle, test:[{title:cnTitle}]} = metaData;
 console.log(esTitle, cnTitle);
}
//Output: abc test

以上这篇基于ES6作用域和解构赋值详解就是小编分享给大家的全部内容了,希望能给大家一个参考,也希望大家多多支持。