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完美解决JavaScript浮点数运算的坑!0.1+0.2=0.30000000000000004?

从一则趣图开始

一群 JS 工程师,实现了一个两数相加的方法

↓↓↓

 

度娘一番,得到以下结果

JavaScript小数在做四则运算时,精度会丢失,这会在项目中引起诸多不便,先请看下面脚本:

<script type="text/javascript" language="javascript">
alert(1/3);//弹出: 0.3333333333333333
alert(0.09999999 + 0.00000001);//弹出: 0.09999999999999999
alert(-0.09999999 - 0.00000001);//弹出: -0.09999999999999999
alert(0.012345 * 0.000001);//弹出: 1.2344999999999999e-8
alert(0.000001 / 0.0001);//弹出: 0.009999999999999998
</script>
<script type="text/javascript" language="javascript"> alert(1/3);//弹出: 0.3333333333333333 alert(0.09999999 + 0.00000001);//弹出: 0.09999999999999999 alert(-0.09999999 - 0.00000001);//弹出: -0.09999999999999999 alert(0.012345 * 0.000001);//弹出: 1.2344999999999999e-8 alert(0.000001 / 0.0001);//弹出: 0.009999999999999998 </script>
<script type="text/javascript" language="javascript">     
    alert(1/3);//弹出: 0.3333333333333333  
    alert(0.09999999 + 0.00000001);//弹出: 0.09999999999999999   
    alert(-0.09999999 - 0.00000001);//弹出: -0.09999999999999999  
    alert(0.012345 * 0.000001);//弹出: 1.2344999999999999e-8  
    alert(0.000001 / 0.0001);//弹出: 0.009999999999999998  
</script>    

按正常计算的话,除第一行外(因为其本身就不能除尽),其他都应该要得到精确的结果,从弹出的结果我们却发现不是我们想要的正确结果。为了解决浮点数运算不准确的问题,在运算前我们把参加运算的数先升级(10的X的次方)到整数,等运算完后再降级(0.1的X的次方)。现收集并整理贴于此,以备后用。

//加法
Number.prototype.add = function(arg){
var r1,r2,m;
try{r1=this.toString().split(".")[1].length}catch(e){r1=0}
try{r2=arg.toString().split(".")[1].length}catch(e){r2=0}
m=Math.pow(10,Math.max(r1,r2))
return (this*m+arg*m)/m
}
//减法
Number.prototype.sub = function (arg){
return this.add(-arg);
}
//乘法
Number.prototype.mul = function (arg)
{
var m=0,s1=this.toString(),s2=arg.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
Number.prototype.div = function (arg){
var t1=0,t2=0,r1,r2;
try{t1=this.toString().split(".")[1].length}catch(e){}
try{t2=arg.toString().split(".")[1].length}catch(e){}
with(Math){
r1=Number(this.toString().replace(".",""))
r2=Number(arg.toString().replace(".",""))
return (r1/r2)*pow(10,t2-t1);
}
}
//加法 Number.prototype.add = function(arg){ var r1,r2,m; try{r1=this.toString().split(".")[1].length}catch(e){r1=0} try{r2=arg.toString().split(".")[1].length}catch(e){r2=0} m=Math.pow(10,Math.max(r1,r2)) return (this*m+arg*m)/m } //减法 Number.prototype.sub = function (arg){ return this.add(-arg); } //乘法 Number.prototype.mul = function (arg) { var m=0,s1=this.toString(),s2=arg.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 Number.prototype.div = function (arg){ var t1=0,t2=0,r1,r2; try{t1=this.toString().split(".")[1].length}catch(e){} try{t2=arg.toString().split(".")[1].length}catch(e){} with(Math){ r1=Number(this.toString().replace(".","")) r2=Number(arg.toString().replace(".","")) return (r1/r2)*pow(10,t2-t1); } }
//加法  
Number.prototype.add = function(arg){  
    var r1,r2,m;  
    try{r1=this.toString().split(".")[1].length}catch(e){r1=0}  
    try{r2=arg.toString().split(".")[1].length}catch(e){r2=0}  
    m=Math.pow(10,Math.max(r1,r2))  
    return (this*m+arg*m)/m  
}  
  
//减法  
Number.prototype.sub = function (arg){  
    return this.add(-arg);  
}  
  
//乘法  
Number.prototype.mul = function (arg)  
{  
    var m=0,s1=this.toString(),s2=arg.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  
Number.prototype.div = function (arg){  
    var t1=0,t2=0,r1,r2;  
    try{t1=this.toString().split(".")[1].length}catch(e){}  
    try{t2=arg.toString().split(".")[1].length}catch(e){}  
    with(Math){  
        r1=Number(this.toString().replace(".",""))  
        r2=Number(arg.toString().replace(".",""))  
        return (r1/r2)*pow(10,t2-t1);  
    }  
}  

测试一把

<script type="text/javascript" language="javascript">
/*
alert(0.09999999 + 0.00000001);//弹出: 0.09999999999999999
alert(-0.09999999 - 0.00000001);//弹出: -0.09999999999999999
alert(0.012345 * 0.000001);//弹出: 1.2344999999999999e-8
alert(0.000001 / 0.0001);//弹出: 0.009999999999999998
*/
alert(Number(0.09999999).add(0.00000001));//弹出: 0.1
//注意,如果是负数,一定要先使用Number转型,否则结果不正确
alert(Number(-0.09999999).sub(0.00000001));//弹出: -0.1
alert(Number(0.012345).mul(0.000001));//弹出: 1.2345e-8
alert(Number(0.000001).div(0.0001));//弹出: 0.01
</script>
<script type="text/javascript" language="javascript"> /* alert(0.09999999 + 0.00000001);//弹出: 0.09999999999999999 alert(-0.09999999 - 0.00000001);//弹出: -0.09999999999999999 alert(0.012345 * 0.000001);//弹出: 1.2344999999999999e-8 alert(0.000001 / 0.0001);//弹出: 0.009999999999999998 */ alert(Number(0.09999999).add(0.00000001));//弹出: 0.1 //注意,如果是负数,一定要先使用Number转型,否则结果不正确 alert(Number(-0.09999999).sub(0.00000001));//弹出: -0.1 alert(Number(0.012345).mul(0.000001));//弹出: 1.2345e-8 alert(Number(0.000001).div(0.0001));//弹出: 0.01 </script>
<script type="text/javascript" language="javascript">  
  
    /* 
     alert(0.09999999 + 0.00000001);//弹出: 0.09999999999999999 
     alert(-0.09999999 - 0.00000001);//弹出: -0.09999999999999999 
     alert(0.012345 * 0.000001);//弹出: 1.2344999999999999e-8 
     alert(0.000001 / 0.0001);//弹出: 0.009999999999999998 
    */  
     alert(Number(0.09999999).add(0.00000001));//弹出: 0.1  
   //注意,如果是负数,一定要先使用Number转型,否则结果不正确  
    alert(Number(-0.09999999).sub(0.00000001));//弹出: -0.1  
   alert(Number(0.012345).mul(0.000001));//弹出: 1.2345e-8  
   alert(Number(0.000001).div(0.0001));//弹出: 0.01  
  
</script>  

 

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