Why Developers Avoid Using `setInterval` in JavaScript

3 min readJul 25, 2025

JavaScript provides several tools for running code at specific intervals. One of the most familiar is setInterval. At first glance, it seems like an easy way to repeat a task every few milliseconds. But as projects grow in complexity, setInterval can cause more harm than good.

In this post, we’ll explore why developers often avoid setInterval, when it’s still useful, and safer alternatives you should consider using instead.

What is `setInterval`?

setInterval runs a function repeatedly at a specified interval (in milliseconds).

setInterval(() => {
  console.log("Runs every second");
}, 1000);

It keeps executing every second, no matter what else is going on in your code. That simplicity is both its strength and its weakness.

Why Developers Avoid `setInterval`

1. It Doesn’t Wait for the Previous Call to Finish

The most common pitfall is that setInterval doesn’t wait for your callback to complete. If your task takes longer than the interval you’ve defined, your code can start overlapping executions.

setInterval(() => {
  fetchData(); // What if this takes 2 seconds?
}, 1000);

This can result in multiple fetchData() calls running simultaneously, leading to network congestion, duplicate results, or unexpected bugs.

2. Timer Drift and Execution Delay

JavaScript is single-threaded. If something else blocks the main thread — like heavy DOM operations or large calculations — setInterval might not execute exactly on schedule. Over time, this can cause drift and unpredictable behavior.

3. Forgetting to Cancel It

Every setInterval returns an ID that you need to store and clear when you're done. If you forget to call clearInterval, it will continue running in the background indefinitely.

const intervalId = setInterval(doSomething, 1000);

// Later
clearInterval(intervalId);

This is particularly important in single-page applications or React/Vue components, where intervals can persist even after the component is unmounted.

When Should You Use `setInterval`?

setInterval can still be useful in cases where:

The task is lightweight and fast
You don’t care about exact timing
You’re not performing asynchronous operations
You’re confident it won’t overlap

Examples include updating a clock, logging status information, or showing periodic UI animations.

Safer Alternatives

1. Recursive `setTimeout`

Using setTimeout recursively lets you control when the next call happens, and ensures the current one is finished first.

function repeat() {
  doSomething();
  setTimeout(repeat, 1000);
}

repeat();

This guarantees there’s a 1-second delay after the task completes.

2. `async/await` with `setTimeout`

For asynchronous tasks like API calls, you can combine await with a setTimeout delay.

async function repeatAsync() {
  while (true) {
    await fetchData();
    await new Promise(resolve => setTimeout(resolve, 1000));
  }
}

repeatAsync();

This avoids overlapping network requests and allows natural pacing.

A Real-World Refactor Example

Let’s say you want to process a list of posts, one per second, until they’re all processed.

Avoid this:

setInterval(() => {
  if (postList.length > 0) {
    callNextPage();
  }
}, 1000);

This risks calling callNextPage multiple times before the previous one finishes.

Use this instead:

async function processPosts() {
  while (postList.length > 0) {
    await callNextPage();
    await new Promise(resolve => setTimeout(resolve, 1000));
  }
}

processPosts();

Now, each page is loaded sequentially, with a delay between each one, and no risk of overlapping calls.

Conclusion

setInterval seems simple, but in practice, it's often too blunt a tool for real-world applications.

It runs code blindly at fixed intervals without understanding how long your code takes or whether it's safe to start again.

You should avoid setInterval when:

Your task is asynchronous or long-running
You need precise control over timing
You want to avoid overlapping executions

Prefer alternatives like recursive setTimeoutandasync/await loops depending on the context.

Still want to use setInterval? Make sure:

Your task is fast and non-blocking
You store the interval ID
You cancel it at the right time

With a bit of planning, you’ll avoid common pitfalls and write more reliable, efficient code.

—

Hope This Helps!!

Cheers!!

Sangwin Gawande

About me : https://sangw.in

Why Developers Avoid Using setInterval in JavaScript

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