vue封装公共方法处理js计算科学记数法精度问题

声明：本文核心是很早之前参考其他大牛的文章或博客，文章出处也找不到了，如有看到请留言，会补上出处。自己稍作改动，一直保留在用。

废话不多说，下面直接上在vue中自己如何使用的代码：

1.新建公共方法的js文件，我为这个单独建了一个文件：

calculation.js 代码：

var countDecimals = function(num) {
    var len = 0;
    try {
        num = Number(num);
        var str = num.toString().toUpperCase();
        if (str.split('E').length === 2) { // scientific notation
            var isDecimal = false;
            if (str.split('.').length === 2) {
                str = str.split('.')[1];
                if (parseInt(str.split('E')[0]) !== 0) {
                    isDecimal = true;
                }
            }
            let x = str.split('E');
            if (isDecimal) {
                len = x[0].length;
            }
            len -= parseInt(x[1]);
        } else if (str.split('.').length === 2) { // decimal
            if (parseInt(str.split('.')[1]) !== 0) {
                len = str.split('.')[1].length;
            }
        }
    } catch (e) {
        throw e;
    } finally {
        if (isNaN(len) || len < 0) {
            len = 0;
        }
        return len;
    }
};

var convertToInt = function(num) {
    num = Number(num);
    var newNum = num;
    var times = countDecimals(num);
    var temp_num = num.toString().toUpperCase();
    if (temp_num.split('E').length === 2) {
        newNum = Math.round(num * Math.pow(10, times));
    } else {
        newNum = Number(temp_num.replace(".", ""));
    }
    return newNum;
};

var getCorrectResult = function(type, num1, num2, result) {
    var temp_result = 0;
    switch (type) {
        case "add":
            temp_result = num1 + num2;
            break;
        case "sub":
            temp_result = num1 - num2;
            break;
        case "div":
            temp_result = num1 / num2;
            break;
        case "mul":
            temp_result = num1 * num2;
            break;
    }
    if (Math.abs(result - temp_result) > 1) {
        return temp_result;
    }
    return result;
};
export default {
    //加法
    accAdd(num1, num2) {
        num1 = Number(num1);
        num2 = Number(num2);
        var dec1, dec2, times;
        try { dec1 = countDecimals(num1) + 1; } catch (e) { dec1 = 0; }
        try { dec2 = countDecimals(num2) + 1; } catch (e) { dec2 = 0; }
        times = Math.pow(10, Math.max(dec1, dec2));
        // var result = (num1 * times + num2 * times) / times;
        var result = (this.accMul(num1, times) + this.accMul(num2, times)) / times;
        return getCorrectResult("add", num1, num2, result);
        // return result;
    },
    //减法
    accSub(num1, num2) {
        num1 = Number(num1);
        num2 = Number(num2);
        var dec1, dec2, times;
        try { dec1 = countDecimals(num1) + 1; } catch (e) { dec1 = 0; }
        try { dec2 = countDecimals(num2) + 1; } catch (e) { dec2 = 0; }
        times = Math.pow(10, Math.max(dec1, dec2));
        // var result = Number(((num1 * times - num2 * times) / times);
        var result = Number((this.accMul(num1, times) - this.accMul(num2, times)) / times);
        return getCorrectResult("sub", num1, num2, result);
        // return result;
    },
    //除法
    accDiv(num1, num2) {
        num1 = Number(num1);
        num2 = Number(num2);
        var t1 = 0,
            t2 = 0,
            dec1, dec2;
        try { t1 = countDecimals(num1); } catch (e) {}
        try { t2 = countDecimals(num2); } catch (e) {}
        dec1 = convertToInt(num1);
        dec2 = convertToInt(num2);
        var result = this.accMul((dec1 / dec2), Math.pow(10, t2 - t1));
        return getCorrectResult("div", num1, num2, result);
        // return result;
    },
    //乘法
    accMul(num1, num2) {
        num1 = Number(num1);
        num2 = Number(num2);
        var times = 0,
            s1 = num1.toString(),
            s2 = num2.toString();
        try { times += countDecimals(s1); } catch (e) {}
        try { times += countDecimals(s2); } catch (e) {}
        var result = convertToInt(s1) * convertToInt(s2) / Math.pow(10, times);
        return getCorrectResult("mul", num1, num2, result);
        // return result;
    }
}

2.在main.js 引入

import cal from './utils/calculation'
Vue.prototype.cal = cal

3.组件中使用

//加法
this.cal.accAdd(2,1);
//减法
this.cal.accSub(2,1);
//除法
this.cal.accDiv(2,1);
//乘法
this.cal.accMul(2,1);

console.log(this.cal.accAdd(2,1))   // 3
console.log(this.cal.accSub(2,1))   // 1
console.log(this.cal.accDiv(2,1))   // 2
console.log(this.cal.accMul(2,1))   // 2