ES6 deconstruction assignment

Deconstruct assignment ： Extract values from arrays and objects according to a certain pattern to assign values to variables .

One 、 An array of deconstruction

When the array is deconstructed and assigned, the corresponding assignment is performed according to the index , Pay attention to the order

（1） One dimensional array

        let arr = [1,2,3];
        let [a,b,c] = arr;
        console.log(a,b,c);//1,2,3

（2） Two dimensional array

        let arr = [1,2,[3,4]];
        let [a,b,c] = arr;
        console.log(a,b,c);//1 2 (2) [3, 4]

        let arr = [1,2,[3,4]];
        let [a,b,[c]] = arr;
        console.log(a,b,c);//1 2 3

（3） The variables accepted on the left have no corresponding variables on the right

        let arr = [1,2,[3,4]];
        let [a,b,[c],d] = arr;
        console.log(a,b,c,d);//1 2 3 undefined

（4） Set the default value

        let arr = [1,2,[3,4]];
        let [a,b,[c],d = 5] = arr;
        console.log(a,b,c,d);//1 2 3 5

Two 、 Object to deconstruct

Assign values according to the key of the object , Random order

（1）

        let hero = {
            name:"Asia",
            age:23
        }
        
        let {name,age} = hero;
        console.log(name,age);//Asia 23

  Left shift sequence

        let hero = {
            name:"Asia",
            age:23
        }
        
        let {age,name} = hero;
        console.log(name,age);//Asia 23

（2） Define an alias

        let hero = {
            name:"Asia",
            age:23
        }
        
        let {age:age2,name:name2} = hero;
        console.log(name2,age2);//Asia 23

3、 ... and 、 String deconstruction assignment

Deconstruct in the same order as an array

        let str = " Face the wind ! Hassa gave ！"
        let [a,b,c,d,e,f,g,h,i,j,k,l,m,n] = str;
        console.log(a,b,c,d,e,f,g,h,i,j,k,l,m,n);// Noodles Yes disease wind Well ! Ha scatter to ！ undefined undefined undefined undefined

  Four 、 Function parameter deconstruction assignment

        function fn([a,b,c]){
            console.log(a,b,c);
        }
        fn([1,2,3]);//1 2 3

  5、 ... and 、JSON Deconstruct assignment

        let json = '{"name":"Asia","age":20}';
        let {name,age} = JSON.parse(json);
        console.log(name,age);//Asia 20