哪位大神教教我这段JavaScript代码s.sort(function(a,b){return a-b;});中的function怎么理解，其中s是数
这个函数是升序排序,如果想逆序排序改成return b-a;就行了.
它的排序原理是每2个数比较,然后根据正负更改数组内元素的位置.
比如第一次比较,a就是888,b就是2222然后返回888-2222 是负的 位置不变.
你可以在函数里面alert一下a和b的值看看.
改了下,可以看到排序过程,看看就知道了
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟</title>
</head>
<body>
<p id="demo">单击按钮降序排列数组。</p>
<p id="debug">测试效果</p>
<button onclick="myFunction()">点我</button>
<script>
function myFunction(){
var points = [40,100,1,5,25,10];
points.sort(function(a,b){document.getElementById("debug").innerHTML +="a为"+a+"b为"+b+"结果为"+(b-a)+(function(){if (b-a<0){return "不动"} else {return "调换"}}()) +"<br>";return b-a});
var x=document.getElementById("demo");
x.innerHTML=points;
}
</script>
</body>
</html>
888, 2222, 9, 4 ·······return 9-888=-879 为负数（为什么和888比较而不和2222比较，因为这是一种折半比较，前面的位数是偶数/2，若前面是奇数/2 +1，此时是偶数，所以和第一位进行比较），9直接挪到888的前面（因为888和2222的关系已经明确，比888小就直接挪到888前面了）
9, 888, 2222, 4 ·······return 4-888=-884为负数，将4挪到888前面
9, 4, 888, 2222········return 4-9=-5为负数，将4挪到9前面
4, 9, 888, 2222·······完成 ,以上数据亲测有效
以上注释为我的推测，有错请指正，不用走流程 (￣3￣)a
The Compare Function
The purpose of the compare function is to define an alternative sort order.
The compare function should return a negative, zero, or positive value, depending on the arguments:
function(a, b){return a-b}
When the sort() function compares two values, it sends the values to the compare function, and sorts the values according to the returned (negative, zero, positive) value.
Example:
When comparing 40 and 100, the sort() method calls the compare function(40,100).
The function calculates 40-100, and returns -60 (a negative value).
The sort function will sort 40 as a value lower than 100.
You can use this code snippet to experiment with numerically and alphabetically sorting:
<button onclick="myFunction1()">Sort Alphabetically</button>
<button onclick="myFunction2()">Sort Numerically</button>
<p id="demo"></p>
<script>
var points = [40, 100, 1, 5, 25, 10];
document.getElementById("demo").innerHTML = points;
function myFunction1() {
points.sort();
document.getElementById("demo").innerHTML = points;
}
function myFunction2() {
points.sort(function(a, b){return a - b});
document.getElementById("demo").innerHTML = points;
}
</script>
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