Round Down

//数値を切り捨てる
	function roundDown(value,num){
		var a,b,c,i;
		a = String(value);
		b = a.indexOf('.');
		c = a.length;
		if (num==0)
			{
			if (b!=-1)
				a = a.substring(0,b);
			}
		else
			{
			if (b==-1)
				{
				a = a + ".";
				for (i=1;i<=num;i++)
					a = a + "0";
				}
			else
				{
				a = a.substring(0,b+num+1);
				for (i=c;i<=b+num;i++)
					a = a + "0";
				}
			}
		return a;
	}
 
roundDown(123.45,1);  // 123.4
roundDown(123.45,0);  // 123