Math.log()
The Math.log()
function returns the natural logarithm
(base e
) of a number, that is
The JavaScript Math.log()
function is equivalent to
ln(x) in mathematics.
Syntax
Math.log(x)
Parameters
x
-
A number.
Return value
Description
If the value of x
is 0, the return value is always
-Infinity
.
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).
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).
Examples
Using Math.log()
Math.log(-1); // NaN, out of range
Math.log(0); // -Infinity
Math.log(1); // 0
Math.log(10); // 2.302585092994046
Using Math.log() with a different base
The 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.
Specifications
Specification |
---|
ECMAScript Language Specification # sec-math.log |
Browser compatibility
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