js計算精度丟失，vue公共方法封裝

最近作後臺管理時候，有大量的輸入計算，可是js自己計算會存在精度丟失，查了一些資料封裝了一個公用的方法，全局使用

1.新建calculation.js文件

var countDecimals = function(num) {    
    var len = 0;    
    try {        
        num = Number(num);        
        var str = num.toString().toUpperCase();        
        if (str.split('E').length === 2) {             
            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) {           
            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 = (this.accMul(num1, times) + this.accMul(num2, times)) / times;        
        return getCorrectResult("add", num1, num2, result);    
    },    
    //減法    
    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((this.accMul(num1, times) - this.accMul(num2, times)) / times);        
        return getCorrectResult("sub", num1, num2, 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);    
    },    
    //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);    
    }
}複製代碼

2.在main.js裏面引入，而且全局註冊

import cal from '@/utils/calculation';
Vue.prototype.cal = cal複製代碼

3.最後直接在須要的地方進行使用就能夠啦...

this.result = this.cal.accMul(this.num, 0.6);複製代碼