Calculation/app/public/js/number-precision.js

var NP = (function (exports) {
    'use strict';

    /**
     * @desc 解决浮动运算问题，避免小数点后产生多位数和计算精度损失。
     * 问题示例：2.3 + 2.4 = 4.699999999999999，1.0 - 0.9 = 0.09999999999999998
     */
    /**
     * 把错误的数据转正
     * strip(0.09999999999999998)=0.1
     */
    function strip(num, precision) {
        if (precision === void 0) { precision = 12; }
        return +parseFloat(num.toPrecision(precision));
    }
    /**
     * Return digits length of a number
     * @param {*number} num Input number
     */
    function digitLength(num) {
        // Get digit length of e
        var eSplit = num.toString().split(/[eE]/);
        var len = (eSplit[0].split('.')[1] || '').length - (+(eSplit[1] || 0));
        return len > 0 ? len : 0;
    }
    /**
     * 把小数转成整数，支持科学计数法。如果是小数则放大成整数
     * @param {*number} num 输入数
     */
    function float2Fixed(num) {
        if (num.toString().indexOf('e') === -1) {
            return Number(num.toString().replace('.', ''));
        }
        var dLen = digitLength(num);
        return dLen > 0 ? strip(num * Math.pow(10, dLen)) : num;
    }
    /**
     * 检测数字是否越界，如果越界给出提示
     * @param {*number} num 输入数
     */
    function checkBoundary(num) {
        if (_boundaryCheckingState) {
            if (num > Number.MAX_SAFE_INTEGER || num < Number.MIN_SAFE_INTEGER) {
                console.warn(num + " is beyond boundary when transfer to integer, the results may not be accurate");
            }
        }
    }
    /**
     * 精确乘法
     */
    function times(num1, num2) {
        var others = [];
        for (var _i = 2; _i < arguments.length; _i++) {
            others[_i - 2] = arguments[_i];
        }
        if (others.length > 0) {
            return times.apply(void 0, [times(num1, num2), others[0]].concat(others.slice(1)));
        }
        var num1Changed = float2Fixed(num1);
        var num2Changed = float2Fixed(num2);
        var baseNum = digitLength(num1) + digitLength(num2);
        var leftValue = num1Changed * num2Changed;
        checkBoundary(leftValue);
        return leftValue / Math.pow(10, baseNum);
    }
    /**
     * 精确加法
     */
    function plus(num1, num2) {
        var others = [];
        for (var _i = 2; _i < arguments.length; _i++) {
            others[_i - 2] = arguments[_i];
        }
        if (others.length > 0) {
            return plus.apply(void 0, [plus(num1, num2), others[0]].concat(others.slice(1)));
        }
        var baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
        return (times(num1, baseNum) + times(num2, baseNum)) / baseNum;
    }
    /**
     * 精确减法
     */
    function minus(num1, num2) {
        var others = [];
        for (var _i = 2; _i < arguments.length; _i++) {
            others[_i - 2] = arguments[_i];
        }
        if (others.length > 0) {
            return minus.apply(void 0, [minus(num1, num2), others[0]].concat(others.slice(1)));
        }
        var baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
        return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
    }
    /**
     * 精确除法
     */
    function divide(num1, num2) {
        var others = [];
        for (var _i = 2; _i < arguments.length; _i++) {
            others[_i - 2] = arguments[_i];
        }
        if (others.length > 0) {
            return divide.apply(void 0, [divide(num1, num2), others[0]].concat(others.slice(1)));
        }
        var num1Changed = float2Fixed(num1);
        var num2Changed = float2Fixed(num2);
        checkBoundary(num1Changed);
        checkBoundary(num2Changed);
        return times((num1Changed / num2Changed), Math.pow(10, digitLength(num2) - digitLength(num1)));
    }
    /**
     * 四舍五入
     */
    function round(num, ratio) {
        var base = Math.pow(10, ratio);
        return divide(Math.round(times(num, base)), base);
    }
    var _boundaryCheckingState = true;
    /**
     * 是否进行边界检查，默认开启
     * @param flag 标记开关，true 为开启，false 为关闭，默认为 true
     */
    function enableBoundaryChecking(flag) {
        if (flag === void 0) { flag = true; }
        _boundaryCheckingState = flag;
    }
    var index = { strip: strip, plus: plus, minus: minus, times: times, divide: divide, round: round, digitLength: digitLength, float2Fixed: float2Fixed, enableBoundaryChecking: enableBoundaryChecking };

    exports.strip = strip;
    exports.plus = plus;
    exports.minus = minus;
    exports.times = times;
    exports.divide = divide;
    exports.round = round;
    exports.digitLength = digitLength;
    exports.float2Fixed = float2Fixed;
    exports.enableBoundaryChecking = enableBoundaryChecking;
    exports['default'] = index;

    return exports;

}({}));