第5章 解构:使数据访问更便捷

1.对象解构

• 允许默认值

let node = {
    name: 'ylz',
    age: 20
}
let {name, age, value = true} = node;
console.log(name);   // ylz 

• 为不同名局部变量赋值

let node = {
    name: 'ylz',
    age: 20
}
let {myName: name, myAge: age} = node;
console.log(myName);   // ylz 

• 嵌套对象解构

let node = {
    name: 'ylz',
    age: 20,
    son: {
        msg: {
            name: '233'
        }
    }
}
let {son: {msg}} = node;
console.log(msg.name);   // 233

2.数组解构

在ES6中交换变量
let a = 1,
    b = 1;
[a, b] = [b, a];
console.log(a);     // 2
console.log(b);     // 1

3.不定元素

let colors = ['red', 'blue', 'green'];
let [firstColor, ...restColors] = colors;
console.log(restColors.length);

4.数组复制

ES5: 
var colors = ['red', 'green'];
var newColors = colors.concat();
ES6: 
let [...newColors] = colors;

5.解构参数
解构可以用在函数参数的传递过程中, 更加方便

funtion setCookie(name, value, {secure, path, domain, expires} = {}) {
    // 设置cookie的代码
}
setCookie('type', 'js', {
    secure: true,
    expires: 6000
});