How to wait resize end event and then perform an action using JavaScript ?

Last Updated : 20 Jul, 2020

When we resize the browser window, the “resize” event is fired continuously, multiple times while resizing. We want the “resize” event to only be fired once we are done resizing.

Prerequisite: To solve this problem we use two functions:

Example: We will use setTimeout() so that they function in which we want to be fire after resizing waits for 500ms. Now, we keep setTimeout() function in the “resize” event. Right before setTimeout(), we set clearTimeOut() which keeps clearing this setTimeout() timer. Since, the resize event is fired continuously when we resize the window, due to this the clearTimeOut() is also called continuously. Due to this, the function inside setTimeout() does not run until we stop resizing.

HTML Code:

<!DOCTYPE html> 
  
<html lang="en"> 
<head> 
    <meta charset="utf-8" /> 
    <title></title> 
</head> 
  
<body> 
    <!-- div is used to display a message  
         when we are done resizing -->
    <div id="message"></div> 
</body> 
  
</html> 

Javascript Code:

<script> 
    
    // Message variable contains the div object which 
    // is used to display message after we are done resizing 
    var message = document.getElementById("message"); 
    
    // timeOutFunctionId stores a numeric ID which is  
    // used by clearTimeOut to reset timer 
    var timeOutFunctionId; 
 
    // The function that we want to execute after  
    // we are done resizing 
    function workAfterResizeIsDone() { 
        message.innerHTML += "<p>Window Resized</p>"; 
    } 
 
    // The following event is triggered continuously 
    // while we are resizing the window 
    window.addEventListener("resize", function() { 
        
        // clearTimeOut() resets the setTimeOut() timer 
        // due to this the function in setTimeout() is  
        // fired after we are done resizing 
        clearTimeout(timeOutFunctionId); 
        
        // setTimeout returns the numeric ID which is used by 
        // clearTimeOut to reset the timer 
        timeOutFunctionId = setTimeout(workAfterResizeIsDone, 500); 
    }); 
</script> 

Finel Solution: In this section, we will combine the above two sections and perform the task.

Program:

<!DOCTYPE html> 
  
<html lang="en"> 
  
<head> 
    <meta charset="utf-8" /> 
    <title></title> 
</head> 
  
<body> 
    <!-- div is used to display a message  
         when we are done resizing -->
    <div id="message"></div> 
  
    <script> 
        
        // Message variable contains the div object which 
        // is used to display message after we are done resizing 
        var message = document.getElementById("message"); 
        
        // timeOutFunctionId stores a numeric ID which is  
        // used by clearTimeOut to reset timer 
        var timeOutFunctionId; 
  
        // The function that we want to execute after  
        // we are done resizing 
        function workAfterResizeIsDone() { 
            message.innerHTML += "<p>Window Resized</p>"; 
        } 
  
        // The following event is triggered continuously 
        // while we are resizing the window 
        window.addEventListener("resize", function() { 
            
            // clearTimeOut() resets the setTimeOut() timer 
            // due to this the function in setTimeout() is  
            // fired after we are done resizing 
            clearTimeout(timeOutFunctionId); 
            
            // setTimeout returns the numeric ID which is used by 
            // clearTimeOut to reset the timer 
            timeOutFunctionId = setTimeout(workAfterResizeIsDone, 500); 
        }); 
    </script> 
</body> 
  
</html> 

Output:

Note: The code will wait 500ms after we are done resizing to fire the function we want to run after we are done resizing,

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