JS——sort

1、a-b升序

<script>
    var arr = [2, 3, 1, 5, 0];
    function compare(a, b) {
        return a - b;
    }
    console.log(arr.sort(compare));//(5) [0, 1, 2, 3, 5]
</script>

2、b-a降序

<script>
    var arr = [2, 3, 1, 5, 0];
    function compare(a, b) {
        return b - a;
    }
    console.log(arr.sort(compare));//(5) [5, 3, 2, 1, 0]
</script>

3、返回值：1升序，-1降序

<script>
    var arr = [2, 3, 1, 5, 0];
    function compare(a, b) {
        if (a > b) {
            return -1;
        } else if (a < b) {
            return 1;
        } else {
            return 0;
        }
    }
    console.log(arr.sort(compare));//(5) [5, 3, 2, 1, 0]
</script>