How can I specify the base for Math.log() in JavaScript?
"Change of Base" Formula / Identity
The numerical value for logarithm to the base 10 can be calculated with the following identity.
Since Math.log(x) in JavaScript returns the natural logarithm of x (same as ln(x)), for base 10 you can divide by Math.log(10) (same as ln(10)):
function log10(val) { return Math.log(val) / Math.LN10;}Math.LN10 is a built-in precomputed constant for Math.log(10), so this function is essentially identical to:
function log10(val) { return Math.log(val) / Math.log(10);}
Easy, just change the base by dividing by the log(10). There is even a constant to help you
Math.log(num) / Math.LN10;which is the same as:
Math.log(num) / Math.log(10);
You can simply divide the logarithm of your value, and the logarithm of the desired base, also you could override the Math.log method to accept an optional base argument:
Math.log = (function() { var log = Math.log; return function(n, base) { return log(n)/(base ? log(base) : 1); };})();Math.log(5, 10);