vue封装公共方法处理js计算科学记数法精度问题

1、utils文件下新建公共方法calculation.js，直接复制以下代码：

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、在页面中使用

//加法
this.cal.accAdd(55,15);
//减法
this.cal.accSub(55,15);
//除法
this.cal.accDiv(55,15);
//乘法
this.cal.accMul(55,15);