Add CSS Rules to a Stylesheet with JavaScript

The insertRule() helps us add a rule at a defined position in the stylesheet while deleteRule() deletes a specific style on a web page. The following examples illustrate CSS rules that can be added to a stylesheet using JavaScript.

Insert a Rule

To insert a rule at a defined position, use the insertRule() method. The margin, padding, and box-shadow is also set. First, the custom id is set using the getElementById() −

let newSheet = document.getElementById('custom').sheet
let cs = 'p {';
   cs += 'margin: 4%;';
   cs += 'padding: 2%;';
   cs += 'font-size: 22px;';
   cs += 'box-shadow: -10px 4px 0 chartreuse;'
   cs += '}';
newSheet.insertRule(cs, 0);

The custom is the id set using the <style> −

<style type="text/css" id="custom">

Example

Let us see the example to insert a rule on a web page −

Open Compiler
<!DOCTYPE html>
<html>
<head>
   <style type="text/css" id="custom">
      body {
         background-color: silver;
      }
   </style>
</head>
<body>
   <h1>Custom CSS!</h1>
   <p>Woohoo!</p>
   <script>
      let newSheet = document.getElementById('custom').sheet
      let cs = 'p {';
         cs += 'margin: 4%;';
         cs += 'padding: 2%;';
         cs += 'font-size: 22px;';
         cs += 'box-shadow: -10px 4px 0 chartreuse;'
      cs += '}';
      newSheet.insertRule(cs, 0);
   </script>
</body>
</html>

Delete a Rule

To delete a rule at a defined position, use the deleteRule() method. First, set the rule using the insertRule() method. The <h2> border is set for the rule −

let mySheet = document.getElementById('demo').sheet
let cs = 'h2 { border: 2px solid green; }'
mySheet.deleteRule(2);
mySheet.insertRule(cs, 0);

The demo is the id set using the <style> −

<style type="text/css" id="demo">

Example

Let us see the example to delete a rule from a web page −

Open Compiler
<!DOCTYPE html>
<html>
<head>
   <style type="text/css" id="demo">
      div {
         margin: 3%;
         text-align: center;
         background-color: powderblue;
      }
      p {
         box-shadow: 0 0 12px rgba(0,0,0,0.6);
      }
      h2 {
         color: red;
      }
   </style>
</head>
<body>
   <div>
      <h2>Custom CSS!</h2>
      <p>Woohoo!</p>
   </div>
   <script>
      let mySheet = document.getElementById('demo').sheet
      let cs = 'h2 { border: 2px solid green; }'
      mySheet.deleteRule(2);
      mySheet.insertRule(cs, 0);
   </script>
</body>
</html>
Updated on: 2023-11-15T14:10:30+05:30

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