[查看演示] 源码如下
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<script>
//任意位四舍五入
Number.prototype.round=function(n){
//code by windy_sk , seasonx@163.net
if(!/\d/.test(n))return this;
var num = this * Math.pow(10,n);
alert(num);
return Math.round(num)/ Math.pow(10,n);
}
alert((1.237802456).round(3))
//阶乘
Number.prototype.fact=function(){
//code by windy_sk , seasonx@163.net
var num = Math.floor(this);
if(num<0)return NaN;
if(num==0 || num==1)
return 1;
else
return (num*(num-1).fact());
}
alert((4).fact())
</script>
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