Microtasks vs. Macrotasks in the JavaScript Event Loop: What\'s the Difference and When Should I Use Each?

Understanding Microtasks and Macrotasks in the Event Loop

The concepts of microtasks and macrotasks are crucial to comprehending how JavaScript's event loop operates.

Microtasks vs. Macrotasks

Microtasks and macrotasks are different types of tasks executed within the event loop. Every loop iteration involves processing one macrotask followed by executing all queued microtasks. Microtasks can queue additional microtasks while being processed, resulting in a series of subsequent microtask executions.

Importance

The distinction between microtasks and macrotasks has practical implications. Recursive microtasking can delay the execution of the next macrotask, potentially blocking the UI or stalling I/O operations. Node.js's process.nextTick() function implements microtasks, but includes a built-in protection (process.maxTickDepth) to prevent infinite recursions.

Usage Considerations

Choose microtasks when actions need to be performed asynchronously but within a synchronous context (e.g., accessing data or DOM manipulation). Otherwise, opt for macrotasks.

Examples

Macrotasks:

• setTimeout
• setInterval
• setImmediate
• requestAnimationFrame
• I/O operations
• UI rendering

Microtasks:

• process.nextTick
• Promises
• queueMicrotask
• MutationObserver

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