CSSStyleDeclaration setProperty() Method

Last Updated : 14 Jul, 2022

The setProperty() method is used to modify the existing CSS property or set the new CSS in the declaration block.

Syntax: It is used to return the length property.

object.setProperty(propertyname, value, priority)

Parameters: It accepts three parameters:

propertyname: It is a required parameter that contains a string which represents the name of the property to set.
value: It is an optional parameter that contains a string which represents the new value.
priority: It is an optional parameter that contains a string which represents if the priority of the property should be set to important or not.

Example: To show the working of the setProperty() method:

html

<html>
 
<head>
    <style>
        body {
            text-align: center;
        }
         
        h1 {
            color: green;
        }
         
        #p1 {
            color: green;
            font-size: 20;
        }
    </style>
</head>
 
<body>
    <h1>GeeksforGeeks</h1>
 
    <p id="p1">
      setProperty() Method
  </p>
 
    <button onclick="myFunction()">
        Set property
    </button>
 
    <p id="gfg"></p>
 
    <!-- Script to set the property -->
    <script>
        function myFunction() {
            var x = 
              document.styleSheets[0].cssRules[2].style;
           
            x.setProperty("background-color", "black");
        }
    </script>
</body>
 
</html>