LESS CSS Functions
Learner Style Sheet has several built-in functions as well. LESS maps JavaScript code with manipulation of values and uses predefined functions to manipulate HTML elements aspects in the style sheet.
color
Parses a color. It is a string representing a color.
Example: color(“#aaa”);
image-size
Gets the image dimensions from a file.
Example: image-size(“Myfile.png”);
image-width
Gets the image width from a file. This function needs to be implemented by each environment. It is currently only available in the node environment.
Example: image-width(“Myfile.png”);
image-height
Gets the image height from a file. This function needs to be implemented by each environment. It is currently only available in the node environment.
Example: image-height(“Myfile.png”);
convert
Convert a number from one unit into another. The first argument contains a number with units and second argument contains units. If the units are compatible, the number is converted. If they are not compatible, the first argument is returned unmodified.
Compatible unit groups:
lengths: m, cm, mm, in, pt and pc,
time: s and ms,
angle: rad, deg, grad and turn.
Example:
convert(19s, “ms”)
convert(140cm, mm)
convert(28, mm) // incompatible unit types
data-uri
Data uri is uniform resource identifier (URI) schema which gets a resource inline on webpages.
Example:
data-uri(‘../data/image.jpg’);
Output: url(https://medium.com/%E2%80%98data:image/jpeg;base64,bm90IGFjdHVhbGx5IGEganBlZyBmaWxlCg==%E2%80%99);
Output in browser: url(https://medium.com/%E2%80%98../data/image.jpg%E2%80%99);
default
Available only inside guard conditions and returns true only if no other mixin matches, false otherwise.
Example:
.mixin(1) {x: 11}
.mixin(2) {y: 22}
.mixin(@x) when (default()) {z: @x}
div {
.mixin(3);
}
div.special {
.mixin(1);
}
unit
Remove or change the unit of a dimension.
Example: unit(5, px) Output: 5px
get-unit
Returns units of a number. If the argument contains a number with units, the function returns its units. The argument without units results in an empty return value.
Example 1: get-unit(5px) Output: px
Example 2: get-unit(5) Output: //nothing
svg-gradient
svg-gradient is a transition of one color to another. It can add many colors to the same element. The position of first and last specified color are optional, remaining colors must have positions specified. The direction must be one of to bottom, to right, to bottom right, to top right, ellipse or ellipse at center. The direction can be specified as both escaped value ~’to bottom’ and space separated list of words to bottom.
Example: colors stops in list:
div {
@list: red, green 30%, blue;
background-image: svg-gradient(to right, @list);
}
if
Returns one of two values depending on a condition.
Examples:
@some: foo;
div {
margin: if((2 > 1), 0, 3px);
color: if((iscolor(@some)), darken(@some, 10%), black);
}
escape
Applies URL-encoding to special characters found in the input string. These characters are not encoded: ,, /, ?, @, &, +, ‘, ~, ! and $. Most common encoded characters are: \<space\>, #, ^, (, ), {, }, |, :, >, <, ;, ], [ and =. Returns escaped string content without quotes.
Example:
escape(‘a=1’)
Output:
a%3D1
[NOTE: if the parameter is not a string, output is not defined.]
e
String escaping. It expects string as a parameter and return its content as is, but without quotes. It can be used to output CSS value which is either not valid CSS syntax, or uses proprietary syntax which Less doesn’t recognize.
Examp
code: “ms:alwaysHasItsOwnSyntax.For.Stuff()”
filter: e(@mscode);
Output:
filter: ms:alwaysHasItsOwnSyntax.For.Stuff();
%format
The function %(string, arguments …) formats a string. The first argument is string with placeholders. All placeholders start with percentage symbol % followed by letter s,S,d,D,a, or A. Remaining arguments contain expressions to replace placeholders. If you need to print the percentage symbol, escape it by another percentage %%.
Example:
format-a-d: %(“repetitions: %a file: %d”, 1 + 2, “directory/file.less”);
format-a-d-upper: %(‘repetitions: %A file: %D’, 1 + 2, “directory/file.less”);
format-s: %(“repetitions: %s file: %s”, 1 + 2, “directory/file.less”);
format-s-upper: %(‘repetitions: %S file: %S’, 1 + 2, “directory/file.less”);
Output:
format-a-d: “repetitions: 3 file: “directory/file.less””;
format-a-d-upper: “repetitions: 3 file: %22directory%2Ffile.less%22”;
format-s: “repetitions: 3 file: directory/file.less”;
format-s-upper: “repetitions: 3 file: directory%2Ffile.less”;
replace
Replaces a text within a string.
Example:
replace(“Hello, Mars?”, “Mars\?”, “Earth!”);
replace(“One + one = 4”, “one”, “2”, “gi”);
replace(‘This is a string.’, “(string)\.$”, “new $1.”);
replace(~”bar-1″, ‘1’, ‘2’);
Output:
“Hello, Earth!”;
“2 + 2 = 4”;
‘This is a new string.’;
bar-2;
extract
Returns the value at a specified position in a list.
Example: extract(8px dotted red, 2);
Output: dotted
Example:
@list: apple, pear, coconut, orange;
value: extract(@list, 3);
Output:
value: coconut;
length
Returns the number of elements in a value list.
Example: length(1px solid #0080ff);
Output: 3
Example:
@list: “banana”, “tomato”, “potato”, “peach”;
n: length(@list);
Output:
n: 4;
ceil
Rounds up to the next highest integer.
Example: ceil(2.4)
Output: 3
floor
Rounds down to the next lowest integer.
Example: floor(2.6)
Output: 2
percentage
Converts a floating point number into a percentage string.
Example: percentage(0.5)
Output: 50%
round
Applies rounding.
Example 1: round(1.67) Output: 2
Example 2: round(1.67, 1) Output: 1.7
sqrt
Calculates square root of a number. Keeps units as they are.
Example 1: sqrt(25cm)
Output: 5cm
Example 2: sqrt(18.6%)
Output: 4.312771730569565%;
abs
Calculates absolute value of a number. Keeps units as they are.
Example 1: abs(25cm)
Output: 25cm
Example 2: abs(-18.6%)
Output: 18.6%;
sin
Calculates sine function. Assumes radians on numbers without units.
Example:
sin(1); // sine of 1 radian
sin(1deg); // sine of 1 degree
sin(1grad); // sine of 1 gradian
Output:
0.8414709848078965; // sine of 1 radian
0.01745240643728351; // sine of 1 degree
0.015707317311820675; // sine of 1 gradian
asin
Calculates arcsine (inverse of sine) function. Returns number in radians e.g. a number between -π/2 and π/2.
Example:
asin(-0.8414709848078965)
asin(0)
asin(2)
Output:
-1rad
0rad
NaNrad
cos
Calculates cosine function. Assumes radians on numbers without units.
Example:
cos(1) // cosine of 1 radian
cos(1deg) // cosine of 1 degree
cos(1grad) // cosine of 1 gradian
Output:
0.5403023058681398 // cosine of 1 radian
0.9998476951563913 // cosine of 1 degree
0.9998766324816606 // cosine of 1 gradian
acos
Calculates arccosine (inverse of cosine) function. Returns number in radians e.g. a number between 0 and π.
Example:
acos(0.5403023058681398)
acos(1)
acos(2)
Output:
1rad
0rad
NaNrad
tan
Calculates tangent function. Assumes radians on numbers without units.
Example:
tan(1) // tangent of 1 radian
tan(1deg) // tangent of 1 degree
tan(1grad) // tangent of 1 gradian
Output:
1.5574077246549023 // tangent of 1 radian
0.017455064928217585 // tangent of 1 degree
0.015709255323664916 // tangent of 1 gradian
atan
Calculates arctangent (inverse of tangent) function. Returns number in radians e.g. a number between -π/2 and π/2.
Example:
atan(-1.5574077246549023)
atan(0)
round(atan(22), 6) // arctangent of 22 rounded to 6 decimal places
Output:
-1rad
0rad
1.525373rad;
pi
Returns π (pi);
Example:
pi()
Output:
3.141592653589793
pow
Returns the value of the first argument raised to the power of the second argument. Returned value has the same dimension as the first parameter and the dimension of the second parameter is ignored.
Example:
pow(0cm, 0px)
pow(25, -2)
pow(25, 0.5)
pow(-25, 0.5)
pow(-25%, -0.5)
Output:
1cm
0.0016
5
NaN
NaN%
mod
Returns the value of the first argument modulus second argument. Returned value has the same dimension as the first parameter, the dimension of the second parameter is ignored. The function is able to handle also negative and floating point numbers.
Example:
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mod(0cm, 0px)
mod(11cm, 6px);
mod(-26%, -5);
Output:
NaNcm;
5cm
-1%;
min
Returns the lowest of one or more values.
Example 1: min(5, 10);
Output: 5
Example 2: min(3px, 42px, 1px, 16px);
Output: 1px
max
Returns the highest of one or more values.
Example 1: max(5, 10);
Output: 10
Example 2: max(3%, 42%, 1%, 16%);
Output: 42%
Isnumber
Returns true if a value is a number, false otherwise.
Example:
isnumber(#ff0); // false
isnumber(blue); // false
isnumber(“string”); // false
isnumber(1234); // true
isnumber(56px); // true
isnumber(7.8%); // true
isnumber(keyword); // false
isnumber(url(https://medium.com/%E2%80%A6)); // false
isstring
Returns true if a value is a string, false otherwise.
Example:
isstring(#ff0); // false
isstring(blue); // false
isstring(“string”); // true
isstring(1234); // false
isstring(56px); // false
isstring(7.8%); // false
isstring(keyword); // false
isstring(url(https://medium.com/%E2%80%A6)); // false
iscolor
Returns true if a value is a color, false otherwise.
Example:
iscolor(#ff0); // true
iscolor(blue); // true
iscolor(“string”); // false
iscolor(1234); // false
iscolor(56px); // false
iscolor(7.8%); // false
iscolor(keyword); // false
iscolor(url(https://medium.com/%E2%80%A6)); // false
iskeyword
Returns true if a value is a keyword, false otherwise.
Example:
iskeyword(#ff0); // false
iskeyword(blue); // false
iskeyword(“string”); // false
iskeyword(1234); // false
iskeyword(56px); // false
iskeyword(7.8%); // false
iskeyword(keyword); // true
iskeyword(url(https://medium.com/%E2%80%A6)); // false
isurl
Returns true if a value is a url, false otherwise.
Example:
isurl(#ff0); // false
isurl(https://medium.com/blue); // false
isurl(https://medium.com/%E2%80%9Cstring%E2%80%9D); // false
isurl(https://medium.com/1234); // false
isurl(https://medium.com/56px); // false
isurl(https://medium.com/7.8%); // false
isurl(https://medium.com/keyword); // false
isurl(https://medium.com/url(%E2%80%A6)); // true
ispixel
Returns true if a value is a number in pixels, false otherwise.
Example:
ispixel(#ff0); // false
ispixel(blue); // false
ispixel(“string”); // false
ispixel(1234); // false
ispixel(56px); // true
ispixel(7.8%); // false
ispixel(keyword); // false
ispixel(url(https://medium.com/%E2%80%A6)); // false
isem
Returns true if a value is an em value, false otherwise.
Example:
isem(#ff0); // false
isem(blue); // false
isem(“string”); // false
isem(1234); // false
isem(56px); // false
isem(7.8em); // true
isem(keyword); // false
isem(url(https://medium.com/%E2%80%A6)); // false
ispercentage
Returns true if a value is a percentage value, false otherwise.
Example:
ispercentage(#ff0); // false
ispercentage(blue); // false
ispercentage(“string”); // false
ispercentage(1234); // false
ispercentage(56px); // false
ispercentage(7.8%); // true
ispercentage(keyword); // false
ispercentage(url(https://medium.com/%E2%80%A6)); // false
isunit
Returns true if a value is a number in specified units, false otherwise.
Example:
isunit(11px, px); // true
isunit(2.2%, px); // false
isunit(33px, rem); // false
isunit(4rem, rem); // true
isunit(56px, “%”); // false
isunit(7.8%, ‘%’); // true
isunit(1234, em); // false
isunit(#ff0, pt); // false
isunit(“mm”, mm); // false
isrules
Returns true if a value is a ruleset, false otherwise.
Example:
@rules: {
color: red;
}
isruleset(@rules); // true
isruleset(#ff0); // false
isruleset(blue); // false
isruleset(“string”); // false
isruleset(1234); // false
isruleset(56px); // false
isruleset(7.8%); // false
isruleset(keyword); // false
isruleset(url(https://medium.com/%E2%80%A6)); // false
rgb
Creates an opaque color object from decimal red, green and blue (RGB) values. Literal color values in standard HTML/CSS formats may also be used to define colors, for example #ff0000.
Example: rgb(90, 129, 32)
Output: #5a8120
[NOTE: An integer 0-255 or percentage 0-100% is used as parameter value in the function.]
rgba
Creates a transparent color object from decimal red, green, blue and alpha (RGBA) values.
Example: rgba(90, 129, 32, 0.5)
Output: rgba(90, 129, 32, 0.5)
argb
Creates a hex representation of a color in #AARRGGBB format (NOT #RRGGBBAA!). This format is used in Internet Explorer, and .NET and Android development.
Example: argb(rgba(90, 23, 148, 0.5));
Output: #805a1794
hsl
Creates an opaque color object from hue, saturation and lightness (HSL) values.
hue: An integer 0-360 representing degrees. saturation: A percentage 0-100% or number 0-1.
lightness: A percentage 0-100% or number 0-1.
Example: hsl(90, 100%, 50%)
Output: #80ff00
hsla
Creates a transparent color object from hue, saturation, lightness and alpha (HSLA) values.
hue: An integer 0-360 representing degrees. saturation: A percentage 0-100% or number 0-1. lightness: A percentage 0-100% or number 0-1.
alpha: A percentage 0-100% or number 0-1.
Example: hsla(90, 100%, 50%, 0.5)
Output: rgba(128, 255, 0, 0.5)
hsv
Creates an opaque color object from hue, saturation and value (HSV) values. Note that this is a color space available in Photoshop, and is not the same as hsl.
hue: An integer 0-360 representing degrees. saturation: A percentage 0-100% or number 0-1.
value: A percentage 0-100% or number 0-1.
Example: hsv(90, 100%, 50%)
Output: #408000
hsva
Creates a transparent color object from hue, saturation, value and alpha (HSVA) values. Note that this is not the same as hsla, and is a color space available in Photoshop.
hue: An integer 0-360 representing degrees. saturation: A percentage 0-100% or number 0-1. value: A percentage 0-100% or number 0-1.
alpha: A percentage 0-100% or number 0-1.
Example: hsva(90, 100%, 50%, 0.5)
Output: rgba(64, 128, 0, 0.5)
hue
Extracts the hue channel of a color object in the HSL color space.
Example: hue(hsl(90, 100%, 50%))
Output: 90
saturation
Extracts the saturation channel of a color object in the HSL color space.
Example: saturation(hsl(90, 100%, 50%))
Output: 100%
lightness
Extracts the lightness channel of a color object in the HSL color space.
Example: lightness(hsl(90, 100%, 50%))
Output: 50%
hsvhue
Extracts the hue channel of a color object in the HSV color space.
Example: hsvhue(hsv(90, 100%, 50%))
Output: 90
hsvsaturation
Extracts the saturation channel of a color object in the HSV color space.
Example: hsvsaturation(hsv(90, 100%, 50%))
Output: 100%
hsvvalue
Extracts the value channel of a color object in the HSV color space.
Example: hsvvalue(hsv(90, 100%, 50%))
Output: 50%
red
Extracts the red channel of a color object.
Example: red(rgb(10, 20, 30))
Output: 10
green
Extracts the green channel of a color object.
Example: green(rgb(10, 20, 30))
Output: 20
blue
Extracts the blue channel of a color object.
Example: blue(rgb(10, 20, 30))
Output: 30
alpha
Extracts the alpha channel of a color object.
Example: alpha(rgba(10, 20, 30, 0.5))
Output: 0.5
luma
Calculates the luma (perceptual brightness) of a color object. Uses SMPTE C / Rec. 709 coefficients, as recommended in WCAG 2.0. This calculation is also used in the contrast function.
Example: luma(rgb(100, 200, 30))
Output: 44%
luminance
Calculates the value of the luma without gamma correction.
Example: luminance(rgb(100, 200, 30))
Output: 65%
saturate
Increase the saturation of a color in the HSL color space by an absolute amount.
Example: saturate(hsl(90, 80%, 50%), 20%)
Output: #80ff00 // hsl(90, 100%, 50%)
desaturate
Decrease the saturation of a color in the HSL color space by an absolute amount.
Example: desaturate(hsl(90, 80%, 50%), 20%)
Output: #80cc33 // hsl(90, 60%, 50%)
lighten
Increase the lightness of a color in the HSL color space by an absolute amount.
Example: lighten(hsl(90, 80%, 50%), 20%)
Output: #b3f075 // hsl(90, 80%, 70%)
darken
Decrease the lightness of a color in the HSL color space by an absolute amount.
Example: darken(hsl(90, 80%, 50%), 20%)
Output: #4d8a0f // hsl(90, 80%, 30%)
fadein
Decrease the transparency (or increase the opacity) of a color, making it more opaque. Has no effect on opaque colors. To fade in the other direction use fadeout.
Example: fadein(hsla(90, 90%, 50%, 0.5), 10%)
Output: rgba(128, 242, 13, 0.6) // hsla(90, 90%, 50%, 0.6)
fadeout
Increase the transparency (or decrease the opacity) of a color, making it less opaque. To fade in the other direction use fadein.
Example: fadeout(hsla(90, 90%, 50%, 0.5), 10%)
Output: rgba(128, 242, 13, 0.4) // hsla(90, 90%, 50%, 0.4)
