⏱️ setTimeout() and setInterval()

Last Updated: 26th October 2025

JavaScript provides functions to schedule tasks and handle time-based events in the browser.

Hinglish Tip 🗣: Ye functions aise samjho — alarm ya timer jaise tools jo kuch kaam future me ya repeat karne ke liye set karte hain.

🕐 1. setTimeout()

  • Purpose: Execute a function once after a specified delay (in milliseconds).
  • Syntax:
setTimeout(function, delay, arg1, arg2, ...);

Parameters:

  • function → Function to execute

  • delay → Time in milliseconds

  • arg1, arg2,... → Optional arguments for the function

  • Example:

setTimeout(() => {
  console.log("Hello after 2 seconds");
}, 2000);

🕐 2. setInterval()

  • Purpose: Execute a function repeatedly at a specified interval (in milliseconds).
  • Syntax:
setInterval(function, interval, arg1, arg2, ...);

Parameters:

  • function → Function to execute

  • interval → Time in milliseconds between each call

  • arg1, arg2,... → Optional arguments for the function

  • Example:

let count = 0;
let intervalId = setInterval(() => {
  console.log("Count:", count);
  count++;
  if (count > 4) clearInterval(intervalId); // Stop after 5 times
}, 1000);

💡 Note: setInterval() returns an identifier that can be used to stop the interval.

3. Clearing Timers

Stop setTimeout or setInterval using clearTimeout or clearInterval.

let timerId = setTimeout(() => console.log("Won't run"), 5000);
clearTimeout(timerId); // Cancels the timeout

let intervalId = setInterval(() => console.log("Repeating"), 1000);
clearInterval(intervalId); // Stops interval immediately

💡 Quick Practice

  • Use setTimeout to log "Welcome!" after 3 seconds.
  • Use setInterval to log numbers from 1 to 5 every second, then stop.
  • Create a timer using setTimeout and cancel it before it executes.
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