The Math.log()
function returns the natural logarithm (base e) of a number, that is
Math.log(x)
x
If the value of x
is negative, the return value is always NaN.
Because log()
is a static method of Math
, you always use it as Math.log()
, rather than as a method of a Math
object you created (Math
is not a constructor).
Math.log()
Math.log(-1); // NaN, out of range Math.log(0); // -Infinity Math.log(1); // 0 Math.log(10); // 2.302585092994046
Math.log()
with a different baseThe following function returns the logarithm of y
with base x
(ie. ):
function getBaseLog(x, y) { return Math.log(y) / Math.log(x); }
If you run getBaseLog(10, 1000)
it returns 2.9999999999999996
due to floating-point rounding, which is very close to the actual answer of 3.
Created by Mozilla Contributors, license: CC-BY-SA 2.5