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解决js浮点数计算精度丢失问题

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解决前端浮点数之间运算精度丢失问题。

实现1

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// 加
Number.prototype['add'] = function (...arg) {
    var r1, r2, m, result = this;
    arg.forEach(value => {
        try { r1 = result.toString().split(".")[1].length } catch (e) { r1 = 0 }
        try { r2 = value.toString().split(".")[1].length } catch (e) { r2 = 0 }
        m = Math.pow(10, Math.max(r1, r2));
        result = Math.round(result * m + value * m) / m;
    });
    return result;
};
// 减
Number.prototype['sub'] = function (...arg) {
    var r1, r2, m, result = this;
    arg.forEach(value => {
        try { r1 = result.toString().split(".")[1].length } catch (e) { r1 = 0 }
        try { r2 = value.toString().split(".")[1].length } catch (e) { r2 = 0 }
        m = Math.pow(10, Math.max(r1, r2));
        var n = (r1 >= r2) ? r1 : r2;
        result = (Math.round(result * m - value * m) / m).toFixed(n);
    });
    return result;
};
// 乘
Number.prototype['mul'] = function (...arg) {
    var result = this;
    arg.forEach(value => {
        var m = 0, s1 = result.toString(), s2 = value.toString();
        try { m += s1.split(".")[1].length } catch (e) { }
        try { m += s2.split(".")[1].length } catch (e) { }
        result = Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m);
    });
    return result;
};
// 除
Number.prototype['div'] = function (...arg) {
    var result = this;
    arg.forEach(value => {
        var t1 = 0, t2 = 0, r1, r2;
        try { t1 = result.toString().split(".")[1].length } catch (e) { }
        try { t2 = value.toString().split(".")[1].length } catch (e) { }
        r1 = Number(result.toString().replace(".", ""));
        r2 = Number(value.toString().replace(".", ""));
        result = (r1 / r2) * Math.pow(10, t2 - t1);
    });
    return result;
};

使用方式

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// 0.1 + 0.2
console.log(0.1.add(0.2)); // 0.3
 
// 同时支持传入多个参与计算的数
var a = 5;
// a * 2 * 3
console.log(a.mul(2, 3)); // 30

实现2

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const calc = {
    //加法
    add :  function (arg1,arg2){ 
      var r1,r2,m; 
      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)); 
      return (arg1*m+arg2*m)/m; 
    },

    //减法
    sub : function (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));
      n=(r1>=r2)?r1:r2; 
      return ((arg1*m-arg2*m)/m).toFixed(n); 
    },

    //乘法
    mul : function (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); 
    },

    //除法
    div : function (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){} 
      
      r1=Number(arg1.toString().replace(".","")); 
      r2=Number(arg2.toString().replace(".","")); 

      return calc.mul( (r1/r2), Math.pow(10,t2-t1) );
      
    }
}

使用方式

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// 1 + 2.33 
calc.add( 1 , 2.33)

// 6 - 3.33
calc.sub( 6 , 3.33)

// 5 * 2.33
calc.mul( 5 , 2.33 )

// 7 / 4.55
calc.div( 7 , 4.55 )
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