js保留几位小数（四舍五入）

记录代码块，方便以后使用

getFloat = function(num, n) {
	n = n ? parseInt(n) : 0;
	if(n <= 0) {
		return Math.round(num);
	}
	num = Math.round(num * Math.pow(10, n)) / Math.pow(10, n); //四舍五入
	num = Number(num).toFixed(n); //补足位数
	return num;
};
console.log(getFloat('1.0009', 3)); //1.001
console.log(getFloat('1.2', 3)); //1.200

//保留4位小数
    var number = 12.3321432;
    number = String(number).replace(/^(.*\..{4}).*$/,"$1");
    number = Number(number); // number = 12.3321
//保留2位小数
    var reg = /^(.*\..{2}).*$/;
    var number2 = 12.3;
    number2 = String(number2).replace(reg ,"$1");
    number2 = Number(number2); // number2 = 12.3  不足保留位数不补0