Debouncing and Throttling in JavaScript

While working with websites, sometimes certain functions are triggered repeatedly without you realizing it. The repetitive calls of functions can take place in a very short period due to scrolling, resizing the window, or even typing something in a search bar. This results in slowing down your app. In order to avoid this, you can use debouncing and throttling. This helps you to control the speed at which functions are executed and also improves performance.

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’s helpful when you have something like a scroll or resize event that happens very often. 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 five times in just 100 milliseconds, the function won’t run immediately. If the debounce delay is 2000 milliseconds (2 seconds), the function will start running after the user stops clicking and for 2 seconds.

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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. It stops the same function from running again and again in a short time, which can sometimes cause weird behavior or errors.

4. By waiting until the user stops typing or clicking, it feels natural and helps to avoid lag.

Disadvantages of Debouncing

1. Since debouncing waits for the user to stop acting, it can slow down how quickly something responds, like a search showing results.

2. If the user types or clicks quickly, 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. It is hard to choose the right time for delay, too short doesn’t help, and too long feels too laggy. Therefore, you have to test different values to make things right.

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, with events like mousemove or keydown, which occur a lot in a short period of time, throttling helps you to run the function only once in every set amount of time, instead of running it on every tiny movement. This helps to keep your app smooth and prevents overloading.

Throttling is a technique in which, no matter how many times the user fires the event, the attached function will be executed only once in a given time interval. Throttling ensures that the function executes at regular intervals. 

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:

Code:

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. If something important happens between the allowed time intervals, throttling in JavaScript might skip it and not respond right away.

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 difference between Debouncing and Throttling 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. By using these techniques in the correct situations, you can make your apps run faster, make them smoother, and more user-friendly. If you are an aspiring web developer, go through our blog and enroll in our Web Development course.

Debouncing and Throttling in JavaScript – FAQs