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Timer Module

In JavaScript, timers are used to schedule functions to be executed either once after a delay or repeatedly at specified intervals. The primary timer functions are

setTimeout
Executes a function once after a specified delay.

setInterval
Repeatedly executes a function at specified intervals.

clearTimeout
Cancels a setTimeout timer.

clearInterval
Cancels a setInterval timer.

While the basic functionality is the same, there are some differences in how timers are implemented and used in the browser and Node.js environments.

Differences Between Browser and Node.js​

Module Scope​

In Node.js, the Timers API is part of the built-in timers module. While you can use setTimeout or setInterval globally, you can also import them from the timers module for clarity.

import { setTimeout } from 'timers';

Event Loop​

In browser, they run on the main thread, which means long-running timer callbacks can block the UI. Node.js uses its event loop to handle timers, allowing for non-blocking operations. This is more efficient for server-side applications.

Additional Methods​

  • Node.js provides the additional method setImmediate to execute a callback immediately after the current event loop cycle.
setImmediate(() => {
  console.log('This runs immediately after the current event loop cycle');
});
  • Another Node.js-specific method is process.nextTick, which schedules a callback to be executed at the end of the current operation, before the event loop continues.
process.nextTick(() => {
  console.log('This runs before the next event loop iteration');
});