js解构

定义：从一个大的数组或对象中提取个别值使用

1.数组解构

从一个数组中提取想要的个别元素，单独使用

[变量1，变量2，…]=数组

左边不是真数组

变量1=数组[0]     变量2=数组[1]    相对应位置变量将获得数组中的相应值或地址 

            var arr =[

                {pname:"小米",price:4399},

                {pname:"华为",price:4399},

                {pname:"苹果",price:4399},

                {pname:"三星",price:4399}

]

            var p1,p2,p4;

            [p1,p2, ,p4] = arr;

            console.log(p1);  // {pname:"小米",price:4399}

            console.log(p2);  // {pname:"华为",price:4399}

             console.log(p4);  // {pname:"三星",price:4399}

2.对象解构

var xiaomi ={

                name : "小米",

                price : 3455,

                login(){

                    console.log("注册");

},

                loginout(){

                    console.log("注销");

}

}

            var {name:p1,login:p2}=xiaomi;

            console.log(p1);

            p2();

如果需要解构的元素名称和对象属性一样{ upwd, logout }=user

            如果需要提前声明name解构时需要加（）       

var upwd,logout;

                   ({upwd, logout }=user);

3.参数解构

定义函数时将形参装扮为对象

function order({

                zhushi:a="香辣鸡腿堡a",

                xiaochi:b="小吃豆",

                drink:c="可乐"

}){

            console.log(`主食：${a}`)

            console.log(`小吃：${b}`)

            console.log(`饮料：${c}`)

}

        order({});

        console.log("**************");

        order({zhushi:"汉堡",xiaochi:"鸡腿",drink:"豆浆"});

        console.log("**************");

        order({drink:"感冒灵"})

引用方式

定义函数时形参和属性同名可zhushi=”香辣鸡腿堡”