High-precision calculation for javascript,You can call add,sub,mul,div to calculate you variables.

calc.js

/**
 * @fileOverview Javascript high precision calculate
 * @author ra <ra@rockagen.com>
 * @version 0.1
 * @see {@link http://usejsdoc.org|jsdoc}
 * @example
 * 
 * 0.05 + 0.01  //0.060000000000000005
 * 1.0 - 0.42  //0.5800000000000001
 * 4.015 * 100  //401.49999999999994
 * 123.3 / 100 //1.2329999999999999
 *
 * calc.add(0.05, 0.01) //0.06
 * calc.sub(1.0, 0.42)  //0.58
 * calc.mul(4.015, 100) //401.5
 * calc.div(123.3, 100) //1.233
 */

/**
 *@namespace calc
 */

(function(exports){

	/**
	 * Addition
	 * @param {Number} num1
	 * @param {Number} num2
	 * @return {Number} result
	 */
	exports.add=function(num1, num2) {
		var baseNum, baseNum1, baseNum2;
		try {
			baseNum1 = num1.toString().split(".")[1].length;
		} catch (e) {
			baseNum1 = 0;
		}
		try {
			baseNum2 = num2.toString().split(".")[1].length;
		} catch (e) {
			baseNum2 = 0;
		}
		baseNum = Math.pow(10, Math.max(baseNum1, baseNum2));
		return (num1 * baseNum + num2 * baseNum) / baseNum;
	};

	/**
	 * Subtraction
	 * @param {Number} num1
	 * @param {Number} num2
	 * @return {Number} result
	 */
	exports.sub=function(num1, num2) {
		var baseNum, baseNum1, baseNum2;
		var precision;
		try {
			baseNum1 = num1.toString().split(".")[1].length;
		} catch (e) {
			baseNum1 = 0;
		}
		try {
			baseNum2 = num2.toString().split(".")[1].length;
		} catch (e) {
			baseNum2 = 0;
		}
		baseNum = Math.pow(10, Math.max(baseNum1, baseNum2));
		precision = (baseNum1 >= baseNum2) ? baseNum1 : baseNum2;
		return ((num1 * baseNum - num2 * baseNum) / baseNum).toFixed(precision);
	}; 

	/**
	 * Multiplication
	 * @param {Number} num1
	 * @param {Number} num2
	 * @return {Number} result
	 */
	exports.mul=function(num1, num2) {
		var baseNum = 0;
		try {
			baseNum += num1.toString().split(".")[1].length;
		} catch (e) {
		}
		try {
			baseNum += num2.toString().split(".")[1].length;
		} catch (e) {
		}
		return Number(num1.toString().replace(".", "")) * Number(num2.toString().replace(".", "")) / Math.pow(10, baseNum);
	};
	/**
	 * Division
	 * @param {Number} num1
	 * @param {Number} num2
	 * @return {Number} result
	 */
	exports.div=function(num1, num2) {
		var baseNum1 = 0, baseNum2 = 0;
		var baseNum3, baseNum4;
		try {
			baseNum1 = num1.toString().split(".")[1].length;
		} catch (e) {
			baseNum1 = 0;
		}
		try {
			baseNum2 = num2.toString().split(".")[1].length;
		} catch (e) {
			baseNum2 = 0;
		}
		baseNum3 = Number(num1.toString().replace(".", ""));
		baseNum4 = Number(num2.toString().replace(".", ""));
		return (baseNum3 / baseNum4) * (Math.pow(10, baseNum2 - baseNum1));
	};

})(typeof exports === 'undefined'?this.calc={}:exports);

It works!
But, how does this work?