ES6 array

1、 Pseudo array to array

（1）Array.prototype.slice.call()

        let divs = document.getElementsByTagName("div");
        let arr = Array.prototype.slice.call(divs);
        console.log(arr);

 （2）Array.from()

        let arrObj = {
            1:"aa",
            0:"bb",
            length:2
        }
        let arr = Array.from(arrObj);
        console.log(arr);

（3）Array.of()

        let arr = Array.of(1,"a",false,[2,3],{a:"asdf"});
        console.log(arr);

        let arr = Array.of(1,2,3,4);
        console.log(arr);

 2、 Element substitution

（1）arr.copyWithin(i,j1[,j2])    use j1 To j2 Element replacement from i Start with the corresponding element ,j2 Ellipsis j1 To the end

        let arr = [0,1,2,3,4,5,6,7,8,9];
        arr = arr.copyWithin(2,5,7);
        console.log(arr);

（2）arr.fill(newVal[,j1,j2])      use newVal Replacement from j1 To j2 The elements of ,j1,j2 Replace all elements without writing      

        let arr = [0,1,2,3,4,5,6,7,8,9];
        arr = arr.fill("newVal",5,8);
        console.log(arr);

3、 Check whether the element exists

includes(item)

        let arr = [1,2,3,NaN]
        console.log(arr.includes(NaN));

indexOf Can 't detect NaN