js计算精度问题

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来自 https://segmentfault.com/q/1010000005641246
引入插件numbers.js、math.js、decimal.js(比较影响编译速度)
以下是加减乘除解决方案

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Number.prototype.add = function (arg) {
    return accAdd(this, arg);
};
Number.prototype.sub = function (arg) {
    return accSub(this, arg);
};
Number.prototype.mul = function (arg) {
    return accMul(this, arg);
};
Number.prototype.div = function (arg) {
    return accDiv(this, arg);
};

function accAdd(arg1, arg2) {
    var r1, r2, m, c;
    try {
        r1 = arg1.toString().split('.')[1].length;
    }
    catch (e) {
        r1 = 0;
    }
    try {
        r2 = arg2.toString().split('.')[1].length;
    }
    catch (e) {
        r2 = 0;
    }
    c = Math.abs(r1 - r2);
    m = Math.pow(10, Math.max(r1, r2));
    if (c > 0) {
        var cm = Math.pow(10, c);
        if (r1 > r2) {
            arg1 = Number(arg1.toString().replace('.', ''));
            arg2 = Number(arg2.toString().replace('.', '')) * cm;
        } else {
            arg1 = Number(arg1.toString().replace('.', '')) * cm;
            arg2 = Number(arg2.toString().replace('.', ''));
        }
    } else {
        arg1 = Number(arg1.toString().replace('.', ''));
        arg2 = Number(arg2.toString().replace('.', ''));
    }
    return (arg1 + arg2) / m;
}

function accSub(arg1, arg2) {
    var r1, r2, m, n;
    try {
        r1 = arg1.toString().split('.')[1].length;
    }
    catch (e) {
        r1 = 0;
    }
    try {
        r2 = arg2.toString().split('.')[1].length;
    }
    catch (e) {
        r2 = 0;
    }
    m = Math.pow(10, Math.max(r1, r2)); //last modify by deeka //动态控制精度长度
    n = (r1 >= r2) ? r1 : r2;
    return ((arg1 * m - arg2 * m) / m).toFixed(n);
}

function accMul(arg1, arg2) {
    var m = 0, s1 = arg1.toString(), s2 = arg2.toString();
    try {
        m += s1.split('.')[1].length;
    }
    catch (e) {
    }
    try {
        m += s2.split('.')[1].length;
    }
    catch (e) {
    }
    return Number(s1.replace('.', '')) * Number(s2.replace('.', '')) / Math.pow(10, m);
}

function accDiv(arg1, arg2) {
    var t1 = 0, t2 = 0, r1, r2;
    try {
        t1 = arg1.toString().split('.')[1].length;
    }
    catch (e) {
    }
    try {
        t2 = arg2.toString().split('.')[1].length;
    }
    catch (e) {
    }
    with (Math) {
        r1 = Number(arg1.toString().replace('.', ''));
        r2 = Number(arg2.toString().replace('.', ''));
        return (r1 / r2) * pow(10, t2 - t1);
    }
}