Debouncing and Throttling in JavaScript

While working with websites, sometimes certain functions are triggered repeatedly without you realizing it. This usually happens during events like scrolling, resizing the browser, or typing in a search bar. This results in slowing down your app. In order to avoid this, you can use debouncing and throttling.  These techniques are widely used for function optimization and efficient event handling, especially to boost JavaScript performance in real-time applications. In this blog, we are going to talk about debouncing in JavaScript and throttling, along with examples, so that you can understand easily. So let’s get started!

Table of Contents

• What is Debouncing?
  • Syntax for Debouncing
  • Advantages of Debouncing
  • Disadvantages of Debouncing
• What is Throttling?
  • Syntax for Throttling
  • Advantages of Throttling
  • Disadvantages of Throttling
• Difference between Debouncing and Throttling in JavaScript
• Conclusion

What is Debouncing?

Debouncing is basically a method in JavaScript where you have to wait for a short time before you run a function. It is useful in situations where events are triggered frequently, like scrolling, resizing, or typing. Instead of running the function every single time the event happens, debouncing makes sure it only runs after the user stops doing the action for a little while. This helps your website run faster and prevents your browser from getting overloaded.

With the debouncing approach, no matter how many times the user triggers an event (like clicking a button), the function will only run after the user stops for a certain amount of time. For example, if someone clicks a button multiple times within 100 milliseconds, and the debounce delay is 2 seconds, the function will only run after the user stops clicking and 2 seconds have passed.

Master Full Stack Development from Scratch

Learn web development, deployment, and application management from the basics

Explore Program

Syntax for Debouncing

The syntax for debouncing in JavaScript is given below for your reference:

function debounce(func, delay) {
    let timer;
    return function (...args) {
        clearTimeout(timer);
        timer = setTimeout(() => func.apply(this, args), delay);
    };
}

A sample code for debouncing in JavaScript is given below for your reference:

Code:

The HTML code, along with the above JS code, is given below:

Code:

Output:

Explanation:

This code creates a text input box that waits for 500 milliseconds after you stop typing before logging the input value to the console using a debounce function.

Advantages of Debouncing

1. Debouncing helps your website run faster by stopping unnecessary function calls that happen too often.

2. It does not send too many requests (API calls) when a user types or clicks quickly. This helps to preserve the resources on the server.

3. Avoids repeated execution of the same function, which can cause errors or lag.

4.  Feels natural for users as the function runs only when they stop interacting.

Disadvantages of Debouncing

1. Responses can feel delayed since the function waits until the user stops interacting.

2. If the user types or clicks continuously, the function may never run. This is because the timer keeps resetting.

3. For things that require instant reaction, like live chats or gaming controls, debouncing helps to make them feel unresponsive.

4.  Choosing the right delay time requires testing, as too little or too much time affects usability.

What is Throttling?

JavaScript throttling is similar to setting a speed limit on the frequency of running a function. Instead of waiting like debouncing does, throttling makes sure the function runs at regular time intervals, even if the user keeps triggering the event again and again.

For example, in events like mousemove or scroll, throttling ensures the function executes only once every defined interval (e.g., every 1000 milliseconds), no matter how many times the event occurs. Throttling is especially useful in scroll performance optimization, where continuous scrolling can trigger hundreds of events per second. Some real-world examples of throttling include limiting API requests, improving scroll tracking in analytics, and controlling window resize events.

Syntax for Throttling

The syntax for throttling in JavaScript is given below for your reference:

function throttle(callback, delay = 1000) {
      let shouldWait = false;
      return (...args) => {
        if (shouldWait) return;
        callback(...args);
        shouldWait = true;
        setTimeout(() => {
              shouldWait = false;
        }, delay);

      };
}

A sample code for throttling in JavaScript is given below for your reference:

Code:

Output:

Explanation:

The above code is used to create a throttled version of the function logMessage. It allows the code to run at most once every 1 second by ignoring the extra calls.

Advantages of Throttling

1. Throttling in JavaScript is used to prevent your app from slowing down. This is done by limiting the number of times the heavy tasks run, like scrolling or resizing.

2. It helps to reduce the number of times a function runs, which saves memory, manages CPU usage, and battery on your device.

3. For the events that occur very quickly, throttling in JavaScript helps to make sure that your function does not get called too often.

4. Throttling also helps to run the functions at regular intervals. This makes the behavior more predictable and hence easier to deal with.

Disadvantages of Throttling

1. Some actions may be ignored if they occur between the fixed time intervals.

2. Since throttling limits the way a function runs, you may feel the response to be a bit delayed, especially in fast interactions with the user.

3. Throttling will always occur after fixed intervals, no matter what, which makes it not as precise in case you want to respond only when a user stops acting.

4. It is hard to find the right time gap. If the interval is short, the function runs too often, and if the interval is too long, it feels laggy. Therefore, you have to test different values to make things right.

Difference between Debouncing and Throttling in JavaScript

The debounce vs throttle difference in JavaScript is given below in tabular format:

Conclusion

Both debouncing in JavaScript and throttling in JavaScript are smart ways to control how often your functions run when users interact with your website. Debouncing can be a good choice for you when you want to wait until the action is finished by the user, like typing or resizing, before doing something. On the other hand, you should use throttling when you want to run a task regularly during continuous actions like scrolling or moving the mouse. Both techniques are essential for frontend optimization and improving overall JavaScript performance during heavy user interactions. By using these techniques in the correct situations, you can make your apps run faster, smoother, and more user-friendly.

Upskill today by enrolling in our Full Stack Web Development Course your next interview by practicing JavaScript Interview Questions prepared by industry experts.

Debouncing and Throttling in JavaScript – FAQs