log (JavaScript)

Gets the natural logarithm (base e) of a number.

Defined in

Math (JavaScript)

Syntax

log(value:double) : double
Parameter Description
value A positive number. See below for special cases.
Return value Description
double The natural logarithm of the parameter.

Usage

Special cases are as follows:
  • The logarithm of NaN or a number less than 0 is NaN.
  • The logarithm of +Infinity is positive infinity.
  • The logarithm of 0 or -0 is negative infinity.

See exp (JavaScript) for the inverse to this method.

To get the logarithm to the base 10 of a number, multiply the return value of this method by LOG10E (JavaScript).

To get the logarithm to the base 2 of a number, multiply the return value of this method by LOG2E (JavaScript).

Examples

(1) This button onclick event calculates the cube root of a number.
sessionScope.result = 
	Math.exp(Math.log(sessionScope.n) / 3)
(2) This button onclick event gets the logarithm of a number to the base 10.
sessionScope.log10 = Math.log(sessionScope.n) * Math.LOG10E
(3) This button onclick event gets the logarithm of a number to the base 2.
sessionScope.log2 = Math.log(sessionScope.n) * Math.LOG2E