sort()问题

Question

<script type="text/javascript">
function sortNumber(a,b){return a - b}
var arr = new Array(3)
arr[0] = "10";
arr[1] = "5";
arr[2] = "4";
document.write(arr + "<br />");
document.write(arr.sort(sortNumber));
</script>

sortNumber(a,b){return a - b}

a-b是什么意思呀 

谢谢

Answer 1

sort()函数通过传入比较函数来排序，在这里return a - b;是说明按从小到大顺序排列