js num 精度计算

//去尾法保留2位小数
public static function toLimit2(num:Number):Number{
			var numS:String = "";
			var str:String = num+"";
			var ar:Array = str.split(".");
			numS += ar[0];
			
			if(ar[1]){
				numS +=".";
				if(String(ar[1]).length>1){
					numS += String(ar[1]).substr(0,2);
				}else{
					numS += String(ar[1]).substr(0,1);
				}
			}
			
			return Number(numS);
		}
		
		//number 加减法
		public static function numAdd(arg1,arg2):Number{
			var r1,r2,m;
			try{r1=arg1.toString().split(".")[1].length}catch(e){r1=0}
			try{r2=arg2.toString().split(".")[1].length}catch(e){r2=0}
			m=Math.pow(10,Math.max(r1,r2))
			return (arg1*m+arg2*m)/m
		}
		
		//number 除法
		public static function numDiv(arg1,arg2):Number{
			var t1=0,t2=0,r1,r2;
			try{t1=arg1.toString().split(".")[1].length}catch(e){}
			try{t2=arg2.toString().split(".")[1].length}catch(e){}
			with(Math){
				r1=Number(arg1.toString().replace(".",""))
				r2=Number(arg2.toString().replace(".",""))
				return (r1/r2)*pow(10,t2-t1);
			}
		}
		
		//number乘法
		public static function numMul(arg1,arg2):Number{
			var m=0,s1=arg1.toString(),s2=arg2.toString();
			try{m+=s1.split(".")[1].length}catch(e){}
			try{m+=s2.split(".")[1].length}catch(e){}
			return Number(s1.replace(".",""))*Number(s2.replace(".",""))/Math.pow(10,m)
		}