getFloat = function(number, n) {
	n = n ? parseInt(n) : 0;
	if(n <= 0) {
		return Math.round(number);
	}
	number = Math.round(number * Math.pow(10, n)) / Math.pow(10, n); //四捨五入
	number = Number(number).toFixed(n); //補足位數
	return number;
};
console.log(getFloat('0', 4)); //0.0000
console.log(getFloat('2.08', 4)); //2.0800
console.log(getFloat('2.08500', 4)); //2.0850
console.log(getFloat('2.08996', 4)); //2.0900
console.log(getFloat('2.08994', 4)); //2.0899