Math.log()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The Math.log()
static method returns the natural logarithm (base e) of a number. That is
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Syntax
Math.log(x)
Parameters
x
-
A number greater than or equal to 0.
Return value
Description
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).
If you need the natural log of 2 or 10, use the constants Math.LN2
or Math.LN10
. If you need a logarithm to base 2 or 10, use Math.log2()
or Math.log10()
. If you need a logarithm to other bases, use Math.log(x) / Math.log(otherBase)
as in the example below; you might want to precalculate 1 / Math.log(otherBase)
since multiplication in Math.log(x) * constant
is much faster.
Beware that positive numbers very close to 1 can suffer from loss of precision and make its natural logarithm less accurate. In this case, you may want to use Math.log1p
instead.
Examples
Using Math.log()
Math.log(-1); // NaN
Math.log(-0); // -Infinity
Math.log(0); // -Infinity
Math.log(1); // 0
Math.log(10); // 2.302585092994046
Math.log(Infinity); // Infinity
Using Math.log() with a different base
The following function returns the logarithm of y
with base x
(i.e. ):
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, but still very close to the actual answer of 3.
Specifications
Specification |
---|
ECMAScript Language Specification # sec-math.log |
Browser compatibility
BCD tables only load in the browser