Alternative for Math.log2

Question

So I have this script that use Javascript's Math.log2() function. Tested it in IE 9 today and found out that IE does not support log2. It only supports log.

Does anyone know of a way that I can get the same result as log base 2? An example of my code is below:

var number = 16,
    exponent = Math.log2(number);

//Will return 4
return exponent;

Answer 1

Expression Math.log(number) / Math.log(2) is equivalent to Math.log2(number)

http://www.mathwords.com/c/change_of_base_formula.htm