Calculation/app/public/js/zh_calc.js

'use strict';

/**
 *
 * @author Mai
 * @date
 * @version
 */
;const zhBaseCalc = (function () {
    const zeroPrecision = 12, mulPrecision = 12, divPrecision = 12;

    function digitLength (num) {
        // 兼容科学计数
        var eSplit = num.toString().split(/[eE]/);
        var len = (eSplit[0].split('.')[1] || '').length - (+(eSplit[1] || 0));
        return len > 0 ? len : 0;
    }

    function powLength (num) {
        var rs = num.toString();
        if (rs.indexOf('+') > 0) {
            return rs.match(/0*$/g).length();
        } else {
            const eSplit = rs.split(/[eE]/);
            const len = Number(eSplit[1]) - this.digitLength(eSplit[0]);
            return len > 0 ? len : 0;
        }
    }

    function round (num, digit) {
        return Math.round(num * Math.pow(10, digit)) / Math.pow(10, digit);
    }

    function add(num1, num2) {
        var d1 = this.digitLength(num1), d2 = this.digitLength(num2);
        return this.round(num1 + num2, Math.max(d1, d2));
    }

    function sub(num1, num2) {
        var d1 = this.digitLength(num1), d2 = this.digitLength(num2);
        return this.round(num1 - num2, Math.max(d1, d2));
    }

    function mul(num1, num2) {
        return this.round(num1 * num2, mulPrecision);
    }

    function div(num1, num2) {
        return this.round(num1 / num2, divPrecision);
    }

    function isNonZero(num) {
        return num && round(num, zeroPrecision) !== 0;
    }

    return {
        digitLength: digitLength,
        powLength: powLength,
        round: round,
        add: add, sub: sub, mul: mul, div: div,
        isNonZero: isNonZero,
    }
})();

/**
 * 计算(四则、舍入) 统一，方便以后置换
 * @type {{add, sub, mul, div, round}}
 */
const ZhCalc = (function () {
    Decimal.set({precision: 50, defaults: true});
    /**
     * 加法 num1 + num2
     * @param num1
     * @param num2
     * @returns {number}
     */
    function add(num1, num2) {
        //return zhBaseCalc.add(num1 ? num1 : 0, num2 ? num2: 0);
        return num1 ? (num2 ? zhBaseCalc.add(num1, num2) : num1) : num2;
    };
    /**
     * 减法 num1 - num2
     * @param num1
     * @param num2
     * @returns {number}
     */
    function sub(num1, num2) {
        return zhBaseCalc.sub(num1 ? num1 : 0, num2 ? num2 : 0);
    }
    /**
     * 乘法 num1 * num2
     * @param num1
     * @param num2
     * @returns {*}
     */
    function mul(num1, num2, digit = 6) {
        //return Decimal.mul(num1 ? num1 : 0, num2 ? num2 : 0).toDecimalPlaces(digit).toNumber();
        return (num1 && num2) ? (Decimal.mul(num1, num2).toDecimalPlaces(digit).toNumber()) : 0;
    }
    /**
     * 除法 num1 / num2
     * @param num1 - 被除数
     * @param num2 - 除数
     * @returns {*}
     */
    function div(num1, num2, digit = 6) {
        if (num2 && !checkZero(num2)) {
            //return Decimal.div(num1 ? num1: 0, num2).toDecimalPlaces(digit).toNumber();
            return num1 ? (Decimal.div(num1, num2).toDecimalPlaces(digit).toNumber()) : 0;
        } else {
            return null;
        }
    }
    /**
     * 四舍五入
     * @param {Number} value - 舍入的数字
     * @param {Number} decimal - 要保留的小数位数
     * @returns {*}
     */
    function round(value, decimal) {
        decimal = decimal ? parseInt(decimal) : 0;
        return value ? new Decimal(value).toDecimalPlaces(decimal).toNumber() : null;
    }

    const ExprCalc = {
        /**
         * 判断value是否是四则运算符
         * @param {String} value - 判断字符串
         * @return {Boolean}
         */
        isOperator(value) {
            const operatorString = "+-*/()";
            return operatorString.indexOf(value) > -1;
        },
        /**
         * Rpn解析栈
         * @param exp
         * @returns {Array}
         */
        parse2Rpn(exp) {
            const getPriority = function (value){
                switch(value){
                    case '+':
                    case '-':
                        return 1;
                    case '*':
                    case '/':
                        return 2;
                    default:
                        return 0;
                }
            };
            const priority = function (o1, o2){
                return getPriority(o1) <= getPriority(o2);
            };

            const inputStack = [];
            const outputStack = [];
            const outputQueue = [];

            for (let i = 0, len = exp.length; i < len; i++) {
                const cur = exp[i];
                if (cur !== ' ' ) {
                    inputStack.push(cur);
                }
            }
            let num = '', isNumPre = false, isOperatorPre = false;
            while(inputStack.length > 0){
                const cur = inputStack.shift();
                if (this.isOperator(cur) && !(cur === '-' && !isNumPre)) {
                    if (isNumPre) {
                        outputQueue.push(parseFloat(num));
                        num = '';
                    }
                    if (cur === '(') {
                        outputStack.push(cur);
                    } else if (cur === ')') {
                        let po = outputStack.pop();
                        while (po !== '(' && outputStack.length > 0) {
                            outputQueue.push(po);
                            po = outputStack.pop();
                        }
                        if (po !== '(') {
                            throw "error: unmatched ()";
                        }
                    } else {
                        while(priority(cur, outputStack[outputStack.length - 1]) && outputStack.length > 0){
                            outputQueue.push(outputStack.pop());
                        }
                        outputStack.push(cur);
                    }
                    isNumPre = false;
                    isOperatorPre = true;
                } else {
                    num = num + cur;
                    isNumPre = true;
                    isOperatorPre = false;
                    if (inputStack.length === 0) {
                        outputQueue.push(parseFloat(num));
                    }
                }
            }
            if (outputStack.length > 0) {
                if (outputStack[outputStack.length - 1] === ')' || outputStack[outputStack.length - 1] === '(') {
                    throw "error: unmatched ()";
                }
                while (outputStack.length > 0) {
                    outputQueue.push(outputStack.pop());
                }
            }
            return outputQueue;
        },
        /**
         * 计算Rpn解析栈
         * @param rpnQueue
         * @returns {*}
         */
        evalRpn(rpnQueue) {
            const getResult = function (num1, num2, opera) {
                switch (opera) {
                    case '+':
                        return add(num1, num1);
                    case '-':
                        return sub(num1, num2);
                    case '*':
                        return mul(num1, num2, 10);
                    case '/':
                        return div(num1, num2, 10);
                    default:
                        throw '参数错误';
                }
            };
            const outputStack = [];
            while(rpnQueue.length > 0){
                const cur = rpnQueue.shift();

                if (!this.isOperator(cur)) {
                    outputStack.push(cur);
                } else {
                    if (outputStack.length < 2) {
                        throw "unvalid stack length";
                    }
                    const sec = outputStack.pop();
                    const fir = outputStack.pop();

                    outputStack.push(getResult(fir, sec, cur));
                }
            }

            if (outputStack.length !== 1) {
                throw "unvalid expression";
            } else {
                return outputStack[0];
            }
        },
        /**
         * 解析四则运算字符串并计算
         * @param {String} expr
         * @returns
         */
        calcExprStrRpn(expr) {
            try {
                if (!isNaN(Number(expr))) {
                    return Number(expr);
                } else {
                    const rpnArr = this.parse2Rpn(expr);
                    const result = this.evalRpn(rpnArr);
                    return result === Infinity ? null : result;
                }
            } catch (err) {
                return null;
            }
        },
    };

    return {add, sub, mul, div, round, isNonZero: zhBaseCalc.isNonZero, calcExpr: ExprCalc}
})();