es6允许从数组中提取值 按照对应位置 对变量赋值 对象也可以实现解构

数组解构

案例1: 左边的[a,r,y]   这个不是数组 而是解构 相当于把1,2,3赋值给了左边对应的a,r,y

    <script>
        let ary = [1, 2, 3]
        let [a, r, y] = [1, 2, 3]
        let [a, r, y] = ary;  //与上面一行同理
        console.log(y);  //3
    </script>

案例2: 如果左边和右边的值 数量不匹配 左边的解构大于右边给的值时 结果返回undefined

   <script>
        let ary = [1, 2, 3]
        let [a, r, y, e, q] = [1, 2, 3]
        console.log(e);  //undefined
    </script>