ConstructionOperation/public/web/scMathUtil.js

/**
 * Created by jimiz on 2017/3/28.
 * 经验证：10000次四舍五入，用num.toFixed为15毫秒，用roundTo为47毫秒，速度低一些，但可以接受
 * 另：经手工验证，用num.toString(2)将十进制浮点数转换为二进制浮点数时，最后一位有错误的情况出现，例子（10.0311）
 */

let scMathUtil = {
    innerRoundTo: function(num, digit){
        let lFactor = Math.pow(10, digit);
        let fOffSet = 0.5;
        let sign = '';
        // 处理符号
        if (num < 0){
            sign = '-';
            num = Math.abs(num);
        }
        // 计算
        let result = Math.floor((num / lFactor) + fOffSet).toString();
        let iLength = result.length;
        // 因为数值被转为整数计算，当目标位数在小数点后，且数值小于0，需要补齐前面的位数
        if (iLength < -digit){
            result = this.zeroString(-digit) + result;
        }
        // 当目标位数在小数点前，需要补齐后面的位数
        else if ((digit > 0) && (iLength < digit)){
            result = result + this.zeroString(digit);
        }
        iLength = result.length;
        // 获得小数点前的数字
        let r1 = result.substring(0, iLength + digit);
        // 获得小数点后的数字
        let r2 = result.substring(iLength + digit, iLength);
        // 拼出完整结果
        return Number(sign + r1 + '.' + r2);
    },
    // 原来直接用num.toString(2)，如果小数段最后位数是0，会被舍掉，导致进位计算bug
    // 改为自己计算二进制，固定为53位。
    // 经验证速度没有差别
    // 另：经手工验证，用num.toString(2)将十进制浮点数转换为二进制浮点数时，最后一位有错误的情况出现，例子（10.0311）
    floatToBin: function(num) {
        let sign = '';
        let dNum = num;
        // 符号位
        if (num < 0) {
            sign = '-';
            dNum = -num;
        };
        // 解析整数段
        let iNum = Math.floor(dNum);
        let iFactor;
        let sResult1 = '';
        // 计算二进制整数段
        while (iNum > 0){
            iFactor = iNum % 2;
            iNum = Math.floor(iNum / 2);
            sResult1 = iFactor + sResult1;
        }
        // 判断是否有整数段
        let bIntZero = sResult1 === '';
        if (bIntZero){
            sResult1 = '0';
        }
        // 解析小数段
        let fNum = dNum - Math.floor(dNum);
        let sResult2 = '';
        if (fNum > 0){
            // 双精度浮点数，尾数总长52位，因为第一位总是1，存储时已经被隐藏，所以有效位数为53位
            const floatLength = 53;

            let iLength;
            // js的bug，浮点数直接取小数可能不能获得精确值，只有转成字符串，截取字符串中的小数段
            let sNum = dNum.toString(10);
            let iDot = sNum.indexOf('.');
            sNum = '0' + sNum.substring(iDot, sNum.length);
            fNum = Number(sNum);
            // 有整数段，则小数位数为全部位数-整数位数
            if (!bIntZero){
                iLength = floatLength - sResult1.length;
            }
            else{
                iLength = floatLength;
            }
            // 计算二进制小数段
            while (iLength > 0){
                fNum = fNum * 2;
                iFactor = Math.floor(fNum);
                fNum = fNum % 1;
                sResult2 = sResult2 + iFactor;
                if (iFactor > 0){
                    bIntZero = false;
                }
                if (bIntZero && (iFactor === 0)){
                    continue;
                }
                iLength--;
            }
        }
        return sign + sResult1 + '.' + sResult2;
    },
    binToFloat: function(bin) {
        let result = 0;
        let iLength = bin.length;
        let sign = '';
        if (iLength > 0 && bin[0]==='-'){
            sign = '-';
            bin = bin.substring(1, iLength);
        }
        iLength = bin.length;
        let iDot = bin.indexOf('.');
        if (iDot >= 0) {
            for (let i = 0; i < iLength; i++) {
                let num = Number(bin[i]);
                let idx = iDot - i;
                if (idx === 0) {
                    continue
                };
                if (idx > 0) {
                    idx -= 1
                };
                let r = Math.pow(2, idx);
                result += num * r;
            }
        }
        else {
            result = parseInt(bin, 2);
        };
        return sign + result;
    },
    zeroString: function(length){
        let result = '';
        for (let i = 0; i < length; i++){
            result = result + '0';
        };
        return result;
    },
    incMantissa: function(bin){
        let result = bin;
        let iDot = bin.indexOf('.');
        if (iDot < 0){return result};
        let iLength = bin.length;
        iLength = bin.length;
        for (let i = iLength - 1; i > iDot; i--){
            let num = Number(bin[i]);
            if (num === 0){
                num = 1;
                let bin1 = bin.substring(0, i);
                let bin2 = this.zeroString(iLength - (i + 1));//bin.substring(i + 1, iLength);
                result = bin1 + num.toString() + bin2;
                break;
            }

        };
        return result;
    },
    roundTo: function(num, digit){
        let me = this;
        return me.innerRoundTo(me.binToFloat(me.incMantissa(me.floatToBin(num))), digit);
    },
    isNumber : function (obj) {
        return obj === +obj;
    },
    roundToString:function(obj,decimal){
        let me = this;
        let value;
        if(me.isNumber(obj)){
            value = me.roundTo(obj,-decimal)
        }else {
            value = me.roundTo(Number(obj),-decimal);
        }
        return value.toFixed(decimal);
    }
};

Number.prototype.toDecimal = function (ADigit) {
    //return parseFloat(this.toFixed(ADigit));
    digit = (ADigit && typeof(ADigit) === 'number' && Number.isInteger(ADigit) && ADigit >= 0) ? -ADigit : -2;
    // var s = scMathUtil.roundTo(this, digit);
    // console.log('Number: ' + this + '   Digit: ' + digit + '    Result: ' + s);
    // return parseFloat(s);
    return scMathUtil.roundTo(this, digit);
};