`sign()` CSS function

The sign() CSS function contains one calculation, and returns -1 if the numeric value of the argument is negative, +1 if the numeric value of the argument is positive, 0⁺ if the numeric value of the argument is 0⁺, and 0⁻ if the numeric value of the argument is 0⁻.

Note: While abs() returns the absolute value of the argument, sign() returns the sign of the argument.

Syntax

css

/* property: sign( expression ) */
top: sign(20vh - 100px);

Parameters

The sign(x) function accepts only one value as its parameter.

x: A calculation which resolves to a number.

Return value

A number representing the sign of A:

If x is positive, returns 1.
If x is negative, returns -1.
If x is positive zero, returns 0.
If x is negative zero, returns -0.
Otherwise, returns NaN.

Formal syntax

<sign()> = 
  sign( <calc-sum> )  

<calc-sum> = 
  <calc-product> [ [ '+' | '-' ] <calc-product> ]*  

<calc-product> = 
  <calc-value> [ [ '*' | / ] <calc-value> ]*  

<calc-value> = 
  <number>        |
  <dimension>     |
  <percentage>    |
  <calc-keyword>  |
  ( <calc-sum> )  

<calc-keyword> = 
  e          |
  pi         |
  infinity   |
  -infinity  |
  NaN

Examples

undefined

Background image position

For example, in background-position positive percentages resolve to a negative length, and vice versa, if the background image is larger than the background area. Thus sign(10%) might return 1 or -1, depending on how the percentage is resolved! (Or even 0, if it's resolved against a zero length.)

css

div {
  background-position: sign(10%);
}

Position direction

Another use case is to control the position of the element. Either a positive or a negative value.

css

div {
  position: absolute;
  top: calc(100px * sign(var(--value)));
}

Specifications

CSS Values and Units Module Level 4

sign() CSS function