Global / Window

`setInterval`

Repeatedly calls a function with a fixed time delay between each call

Syntax

JavaScript

setInterval(callback, delay?, ...args)

Parameters

Parameter	Type	Description
callback	Function	A function to be executed every delay milliseconds
delay	number	Time in milliseconds between each execution
args	any[]	Additional arguments passed to the callback

Return Value

A positive integer ID that identifies the interval (use with clearInterval to cancel)

Examples

Basic Usage

let count = 0;
const id = setInterval(() => {
  count++;
  console.log(`Tick ${count}`);
  if (count >= 5) clearInterval(id);
}, 1000);

Practical Example

function poll(url: string, intervalMs: number) {
  const id = setInterval(async () => {
    const res = await fetch(url);
    const data = await res.json();
    if (data.complete) clearInterval(id);
  }, intervalMs);
  return id;
}

Advanced Usage

const clock = setInterval(() => {
  console.log(new Date().toLocaleTimeString());
}, 1000);

Understanding setInterval

The setInterval method in JavaScript repeatedly calls a function with a fixed time delay between each call. It belongs to the window object and is one of the most widely used methods for working with window values in modern JavaScript and TypeScript applications.

The method signature is setInterval(callback, delay?, ...args). It accepts 3 parameters: callback, delay, args. When called, it returns a positive integer id that identifies the interval (use with clearinterval to cancel). Understanding when and how to use setInterval() helps you write more expressive, readable code.

Common use cases for setInterval include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like window-clearinterval, window-settimeout, window-cleartimeout, enabling you to chain operations together for complex data manipulation pipelines.

Browser support for setInterval is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. It is also fully supported in Node.js and Deno. For older environments, transpilation with Babel or a polyfill may be needed.