JavaScript - Timers (setTimeout, setInterval)

Overview

Estimated time: 15–20 minutes

JavaScript timers let you schedule code to run after a delay or at intervals. Use setTimeout for one-time delays and setInterval for repeated execution.

Learning Objectives

• Use setTimeout and setInterval.
• Clear timers to stop scheduled code.

Prerequisites

• JavaScript - Microtasks & Event Loop

setTimeout

setTimeout(() => {
  console.log('Runs after 1 second');
}, 1000);

setInterval

const id = setInterval(() => {
  console.log('Runs every 2 seconds');
}, 2000);

// To stop:
setTimeout(() => clearInterval(id), 7000);

Common Pitfalls

• Forgetting to clear intervals can cause memory leaks.
• setTimeout and setInterval delays are not guaranteed to be exact.

Summary

Timers are essential for scheduling code in JavaScript. Always clear intervals when no longer needed.