Global / Window

`queueMicrotask`

Queues a microtask to be executed before control returns to the browser's event loop

Syntax

JavaScript

queueMicrotask(callback)

Parameters

Parameter	Type	Description
callback	() => void	The function to be executed as a microtask

Return Value

undefined

Examples

Basic Usage

queueMicrotask(() => {
  console.log('microtask');
});
console.log('sync');
// Output: 'sync', 'microtask'

Practical Example

console.log('1');
setTimeout(() => console.log('4'), 0);
queueMicrotask(() => console.log('2'));
console.log('3');
// Output: 1, 3, 2, 4

Advanced Usage

function flush(tasks: (() => void)[]) {
  while (tasks.length) {
    const task = tasks.shift()!;
    queueMicrotask(task);
  }
}

Understanding queueMicrotask

The queueMicrotask method in JavaScript queues a microtask to be executed before control returns to the browser's event loop. 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 queueMicrotask(callback). It accepts 1 parameter: callback. When called, it returns undefined. Understanding when and how to use queueMicrotask() helps you write more expressive, readable code.

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

Browser support for queueMicrotask 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.