How to dynamically create ‘@-Keyframe’ CSS animations?

In order to dynamically allocate keyframe animations to our HTML web-page, we are going to use the CSS stylesheets insertRule() method. We are going to take keyframes animation from a text area and then we will apply those rules to our web-page.

insertRule() method: This method is use to insert some new CSS rule into the current CSS style sheet(bound with some restriction).

Syntax:

stylesheet.insertRule(rule [, index])

Parameter: The method accepts two parameters as mentioned above and described below:

  • Rule: A DOMstring which is essentially the CSS rule to be inserted.



  • index(optional): The index at which the rule is inserted in CSSStyleSheet.cssRules

Example:

  • HTML: First, let’s make the layout structure of our page using HTML and CSS.

    html

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    <!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8">
      <meta name="viewport" 
            content="width=device-width, 
                     initial-scale=1.0">
    </head>
    <body>
      <h2 style="color: green;">GeeksforGeeks</h2>
      <div id="element"></div>
      <form id="input">
        <textarea id="text" rows="10" cols="40"></textarea><br>
        <button type="submit">ADD ANIMATION</button>
      </form>
      <style>
        #element{
          width: 200px;
          height: 200px;
          background-color: green;
          margin-bottom: 5px;
        }
      </style>
    </body>

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  • Output: The structure will look like.
  • JavaScript: Now, We are going to input a keyframe animation in the text area above and add it to the element that we have created.

    javascript

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    // Javascript code to add keyframes
    let styleSheet = null;
    dynamicAnimation = (name,styles) => {
    // Creating a style element
    // To add the keyframes
    if (!styleSheet){
      styleSheet = document.createElement('style');
      styleSheet.type = 'text/css';
      document.head.appendChild(styleSheet);
    }
    // Adding The Keyframes
    styleSheet.sheet.insertRule(`@keyframes ${name} {${styles}}`,
    styleSheet.length
    );
    }
       
    const form = document.getElementById("input");
    const text = document.getElementById("text");
    form.addEventListener('submit', (e)=>{
      e.preventDefault()
      // Adding an animation
      // NewAnimation, with the 
      // Keyframes to the Stylesheet
      dynamicAnimation('newAnimation', text.value);
      // Timing and duration can be altered
      // As per user requirements
      document.getElementById("element").style.animation = 
      'newAnimation 3s infinite';
    });

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Implementation Code:

html

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" 
        content="width=device-width, 
        initial-scale=1.0">
</head>
<body>
  <h2 style="color: green;">GeeksforGeeks</h2>
  <div id="element"></div>
  <form id="input">
    <textarea id="text" rows="10" cols="40"></textarea><br>
    <button type="submit">ADD ANIMATION</button>
  </form>
  <style>
    #element{
      width: 200px;
      height: 200px;
      background-color: green;
      margin-bottom: 5px;
    }
  </style>
  <script>
    let styleSheet = null;
    dynamicAnimation = (name,styles) => {
    if (!styleSheet){
      styleSheet = document.createElement('style');
      styleSheet.type = 'text/css';
      document.head.appendChild(styleSheet);
    }
  
    styleSheet.sheet.insertRule(`@keyframes ${name} {${styles}}`,
    styleSheet.length
    );
    }
  
    const form = document.getElementById("input");
    const text = document.getElementById("text");
    form.addEventListener('submit', (e)=>{
      e.preventDefault();
      console.log("submitted");
      console.log(text.value);
  
      dynamicAnimation('newAnimation', text.value);
      document.getElementById("element").style.animation = 
                                'newAnimation 3s infinite';
    });
  </script>
</body>
</html>

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CSS:Now, We are going to add the following Keyframe Rule Set to the text box element.

CSS

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25%{
    transform : translateX(25%);
    border-radius : 25%;
   }
50%{
    transform : translateX(50%);
    border-radius : 50%;
   }
75%{
    transform : translateX(25%);
    border-radius : 25%;
}
100%{
    transform : translateX(0%);
    border-radius : 0%;
}

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Output:

  • Before Submitting Keyframes:

  • After Submitting Keyframes:




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