javascript 代码片段

1 select获取改变之前的值

var previous;
$("select").focus(function () {
    // Store the current value on focus, before it changes
    previous = this.value;
}).change(function() {
    // Do something with the previous value after the change
    alert(previous);
});

2 javascript保留两位小数

parseFloat(num).toFixed(2);
//or
Math.round(num * 100) / 100

end