Logarithmic Functions
The basic natural logarithm function is
Math.log
. In some languages, “log” refers to
“log base 10” and “ln” refers to “natural logarithm,” so keep in mind that in JavaScript,
“log” means “natural logarithm.” ES6 introduced
Math.log10
for convenience.
Table 16-2. Logarithmic functions
Function
Description
Examples
Math.log(x)
Natural logarithm of x
Math
.
log
(
Math
.
E
)
// 1
Math
.
log
(
17.5
)
// ~2.86
Math.log10(x)
Base 10 logarithm of x
Equivalent to
Math.log(x)/
Math.log(10)
Math
.
log10
(
10
)
// 1
Math
.
log10
(
16.7
)
// ~1.22
Math.log2(x)
Base 2 logarithm of x
Equivalent to
Math.log(x)/
Math.log(2)
Math
.
log2
(
2
)
// 1
Math
.
log2
(
5
)
// ~2.32
Math.log1p(x)
Natural logarithm of 1 + x
Equivalent to
Math.log(1 + x)
Math
.
log1p
(
Math
.
E
-
1
)
// 1
Math
.
log1p
(
17.5
)
// ~2.92
Miscellaneous
lists miscellaneous numeric functions that allow you to perform common
operations such as finding the absolute value, ceiling, floor, or sign of a number, as
well as finding the minimum or maximum number in a list.
Table 16-3. Number miscellaneous algebraic functions
Function
Description
Examples
Math.abs(x)
Absolute value of x
Math
.
abs
(
-
5.5
)
// 5.5
Math
.
abs
(
5.5
)
// 5.5
Math.sign(x)
The sign of x: if x is negative,
–1; if x is positive, 1; and if x
is 0, 0
Math
.
sign
(
-
10.5
)
// -1
Math
.
sign
(
6.77
)
// 1
Math.ceil(x)
The ceiling of x: the smallest
integer greater than or equal
to x
Math
.
ceil
(
2.2
)
// 3
Math
.
ceil
(
-
3.8
)
// -3
Math.floor(x)
The floor of x: the largest
integer less than or equal to x
Math
.
floor
(
2.8
)
// 2
Math
.
floor
(
-
3.2
)
// -4
Algebraic Functions | 233
