LESS - Type Checking Functions



You can use type checking built-in functions to determine the value types for matching mixins. To do this, you can use the is functions. Following is the list of available functions −

  • iscolor
  • isnumber
  • isstring
  • iskeyword
  • isurl

The functions listed above are into basic type checking. You can check whether a value is in a specific unit or not by using the following functions −

  • ispixel
  • ispercentage
  • isem
  • isunit


The following example demonstrates the use of type checking functions in the LESS file −

<!doctype html>
      <title>Type Checking Functions</title>
      <link rel = "stylesheet" href = "style.css" type = "text/css" />

      <h2>Example of Type Checking Functions</h2>
      <p class = "myclass">Hello World!!!Welcome to Tutorialspoint...</p>

Next, create the style.less file.


.mixin (@a; @b: red) when (iscolor(@b)){

.mixin (@a) {
   font-size: @a;

.myclass { .mixin(20px) }

You can compile the style.less to style.css by using the following command −

lessc style.less style.css

Now execute the above command; it will create the style.css file automatically with the following code −


.myclass {
   color: blue;
   font-size: 20px;


Follow these steps to see how the above code works −

  • Save the above html code in the type_checking_functions.html file.

  • Open this HTML file in a browser, the following output will get displayed.

Mixin Guards