# Method to solve floating point error of multiplication in JS

• 2020-03-30 01:14:01
• OfStack

JS does the decimal multiplication operation when floating point error, specific can be tested:

< Script>
< / script>

The result is 251.89999999999998 instead of 251.9

This must be a headache for many. So what's the solution? Here is the solution.

1.

``````
<script>
</script>
``````

So the general idea here is to make the factor an integer, and then divide it by some multiple, and then you get the right answer.
2,
``````
<script defer>
Number.prototype.rate=function(){
var oStr=this.toString();
if(oStr.indexOf(".")==-1)
return 1;
else
return Math.pow(10,parseInt(oStr.length-oStr.indexOf(".")-1));
}
function tran(){
args=tran.arguments;
var temp=1;
for(i=0;i<args.length;i++)
temp*=args[ i ]*args[ i ].rate();
for(i=0;i<args.length;i++)
temp/=args[ i ].rate();
return temp
}
</script>
``````

The solution is cumbersome, but it gives you an idea of the actual process of solving the problem.

You can also round it off, & PI; Math.round can be used in js to round off integers, and if you need to do this to the exact number of decimal points, you need to write a function.

``````
function ForDight(Dight,How) {
Dight = Math.round(Dight*Math.pow(10,How))/Math.pow(10,How);
return Dight;
}
//Division function, used to get accurate division results
//Note: javascript division results will have errors, in two floating point division will be more obvious. This function returns a more precise division result.
//Call: accDiv (arg1, arg2)
//Return value: the exact result of arg1 divided by arg2
function accDiv(arg1,arg2){
var t1=0,t2=0,r1,r2;
try{t1=arg1.toString().split(".").length}catch(e){}
try{t2=arg2.toString().split(".").length}catch(e){}
with(Math){
r1=Number(arg1.toString().replace(".",""))
r2=Number(arg2.toString().replace(".",""))
return (r1/r2)*pow(10,t2-t1);
}
}
//Add a div method to the Number type to make it easier to call.
Number.prototype.div = function (arg){
return accDiv(this, arg);
}
//The multiplication function, which is used to get exact multiplication results
//Note: javascript multiplication results will have errors, in the two floating point number multiplication will be more obvious. This function returns a more precise multiplication result.
//Call: accMul (arg1, arg2)
//Return value: the exact result of arg1 times arg2
function accMul(arg1,arg2)
{
var m=0,s1=arg1.toString(),s2=arg2.toString();
try{m+=s1.split(".").length}catch(e){}
try{m+=s2.split(".").length}catch(e){}
return Number(s1.replace(".",""))*Number(s2.replace(".",""))/Math.pow(10,m)
}
//Add a mul method to the Number type to make it easier to call.
Number.prototype.mul = function (arg){
return accMul(arg, this);
}
//Note: javascript addition results will have errors, in the two floating point Numbers will be more obvious when adding. This function returns a more accurate addition result.
//Return value: the exact result of arg1 plus arg2
var r1,r2,m;
try{r1=arg1.toString().split(".").length}catch(e){r1=0}
try{r2=arg2.toString().split(".").length}catch(e){r2=0}
m=Math.pow(10,Math.max(r1,r2))
return (arg1*m+arg2*m)/m
}
//Add an add method to the Number type to make it easier to call.