Comments on: Extend Math.round, Math.ceil and Math.floor to allow for precision

By: Lea Verou

Lea Verou — Wed, 01 Apr 2009 03:33:03 +0000

@alexiers: This is precisely what this post is about You can just use the code I posted, or the one Rene Sarsoo posted and then you can do what you want by inputting the decimals as a second parameter. For instance Math.round(3.6789, 2) would return 3.68 after that.

By: alexiers

alexiers — Tue, 31 Mar 2009 23:11:50 +0000

I’m still learning javascript. Mind if I ask some help?

You see, I want to change a value with multiple decimal to just two.
Let’s say the value is 3.6789 and I just want to round it up to the first two decimal like 3.68.

How can it be done? I tried using math.round and ceil and floor but the values end up becoming integers instead.

Would be a big help if you could.

By: Lea Verou

Lea Verou — Mon, 09 Mar 2009 14:17:37 +0000

Thanks for commenting Rene and welcome to my blog!

Good point! Your solution is much better.

I came up with this “trick” a long time ago and I wasn’t really comfortable with closures at the time. I never really revised it since then. I’ll do it your way from now on

By: Rene Saarsoo

Rene Saarsoo — Mon, 09 Mar 2009 13:00:14 +0000

Instead of storing standard Math.round to Math._round, why not hide it completely inside a closure:

Math.round = (function() {
  var oldRound = Math.round;
  return function(number, precision) {
    precision = Math.abs(parseInt(precision)) || 0;
    var coefficient = Math.pow(10, precision);
    return oldRound(number*coefficient)/coefficient;
  };
})();