1.数组（排序，过滤，求和，去重，乱序）

    let array = {}
//sort 数组正序
    array = [5, 4, 3, 2, 1]
    console.log(array.sort())
//reverse  数组倒序
    array = [1, 2, 3, 4, 5]
    console.log(array.reverse())
//filter 数组过滤
    array = [1, 5, 10, 15, 20]