JavaScript Event Loop队列术语辨析：Queue、Message Queue与Event Queue
Great question—this terminology mess is super common, and I’ve seen tons of developers scratch their heads over it too. Let’s break it down clearly:
First, the Standard Definition
The ECMAScript specification (JavaScript’s official rulebook) defines this core queue as the Task Queue (sometimes explicitly called the macrotask queue). This is where "tasks" like DOM event callbacks, setTimeout/setInterval handlers, network request responses, and I/O operations wait until the call stack is empty.
There’s also a separate Job Queue (or microtask queue) for smaller, higher-priority tasks like Promise.then/catch/finally callbacks, MutationObserver handlers, and process.nextTick (in Node.js). The Event Loop processes all microtasks in this queue before picking the next task from the Task Queue—an important distinction, but not the queue you’re asking about here.
Why the Confusion with Terms Like Message Queue/Event Queue?
The terminology chaos comes from a few key places:
- Historical browser implementations: Early browser engines (like Chrome’s V8) referred to this queue as the Message Queue because each task was framed as a "message" sent to the runtime (e.g., "the user clicked a button" is a message, "the timer expired" is another message). This term stuck in countless tutorials and docs.
- Context-specific shorthand: When most tasks in the queue are DOM events (clicks, scrolls, etc.), developers started calling it the Event Queue. But this is a misnomer—timers, network calls, and other non-event tasks also live here, so it’s not accurate for all cases.
- Simplified teaching language: Many beginner-focused resources just call it the Queue to avoid overcomplicating the basics of the Event Loop.
MDN’s Mixing of Terms
MDN’s docs balance strict standard terminology with what developers actually encounter in practice. So you’ll see them switch between "Task Queue", "Message Queue", and "Event Queue" depending on the context—they’re all referring to the same core macrotask queue. The inconsistency is intentional to align with common developer language, even if it’s not 100% strict to the spec.
To Sum Up
- The standard, spec-compliant term is Task Queue (macrotask queue).
- Message Queue, Event Queue, and plain old Queue are all colloquial or context-specific shorthand for the same thing—they’re just implementation/teaching terms that stuck.
- The confusion is totally normal because different resources prioritize either strict spec language or practical, widely used terms.
内容的提问来源于stack exchange，提问作者Flavio Copes
