js sort根据数值大小自动排序（转）

var arrDemo = new Array();

arrDemo[0] = 10;
arrDemo[1] = 50;
arrDemo[2] = 51;
arrDemo[3] = 100;

arrDemo.sort(); //调用sort方法后，数组本身会被改变，即影响原数组

alert(arrDemo);//10,100,50,51 默认情况下sort方法是按ascii字母顺序排序的，而非我们认为是按数字大小排序

arrDemo.sort(function(a,b){return a>b?1:-1});//从小到大排序

alert(arrDemo);//10,50,51,100

arrDemo.sort(function(a,b){return a<b?1:-1});//从大到小排序

alert(arrDemo);//100,51,50,10