# JavaScript round float to n decimal points

The best you can do with built in JavaScript functions is to round a number to the nearest integer using the method Math.round(x), so to round a float to n decimal points we need to come up with our own function.

The function round_float() rounds a floating point number x to n decimals, if you ommit the parameter n, the function will have the same behaviour as the round() method, here is the round_float function definition:

```function round_float(x,n){
if(!parseInt(n))
var n=0;
if(!parseFloat(x))
return false;
return Math.round(x*Math.pow(10,n))/Math.pow(10,n);
}
```

## With prototyping

Dmitry suggested a better approach using prototyping:

```if (!Number.toFixed) {
Number.prototype.toFixed=function(n){
return Math.round(this*Math.pow(10, n)) / Math.pow(10, n);
}
}

// example:
floating_number = 123.45687;
decimal_points = 2;
```

1. Dmitry says:

It would be better to use prototyping here. Newer browsers support toFixed() function. Older don’t.
So here’s the way to do it:

```if (!Number.toFixed) {
Number.prototype.toFixed=function(x) {
var temp=this;
temp=Math.round(temp*Math.pow(10,x))/Math.pow(10,x);
return temp;
}}

example:

f=123.23453

2. Chat says:

make it simpler

```function round(val, prec)
{
return parseFloat(parseFloat(val).toFixed(prec));
}
```
1. Nabil says:

This is very clean, if val is not a number the function will return NaN (Not a Number)

Thanks Chat!