Extending Number.prototype in javascript and the Math object?

Question

I've always wondered why Javascript has the global Math object instead of giving numbers their own methods. Is there a good reason for it?

Also are there any drawbacks (other than efficiency) to doing something like this?:

Number.prototype.round = function(){     return Math.round(this); }; 

Just to make clear, I understand that constants like π need somewhere and functions that are applied on more than one number like min/max. The question was mainly concerning methods which only effect a single number such as round, abs, sin, pow, etc.

Answer 1

The reason for the Math object is simple: "because Java does it". Not the best of reasons, but here we are. I guess things made more sense back then, before Douglas Crockford started his campaign to suppress half the language*. Originally you were "allowed", or meant, to do things like this:

with (Math) {   var n = min( round(a) * round(b), sqrt(c) );   var result = exp( n + d ); } 

The drawback to extending Number.prototype is that someone else might do the same thing. Or worse, for example, define Number.prototype.round as a symmetrical rounding function.

If you are looking for ways to make your life easier, why stop there? Why not simply include Math functions as global functions?

var m = 'abs acos asin atan atan2 ceil cos exp floor log max min ' +         'pow random round sin sqrt tan PI').split(' '); for (var i=0,l=m.length; i<l; i++) {   window[ m[i] ] = Math[ m[i] ]; } 

This will drop all the math functions into the global scope, effectively allowing you to stop typing "Math." Ask yourself: Is there any real difference between extending Number and extending window with these functions?

* Before you flame me: The Crockford comment is not meant to be taken too seriously. I do agree with him that with is very dangerous in an implicit global environment.