JAVASCRIPT GUIDE
JavaScript Event Loop Interview Guide
By the HireReadyAI team · 8 min read
Call stack, task queues, browser vs Node nuances, and practice prompts.
The concurrency model
JavaScript runs on a single call stack. Asynchronous work is scheduled via the event loop, which pulls callbacks from queues when the stack is clear. That is how UI stays responsive and Node handles many sockets without one thread per connection.
Task queues
Macrotasks include setTimeout, setInterval, and I/O callbacks. Microtasks include Promise reactions and queueMicrotask. Microtasks run before the next macrotask. Interview questions often mix these to test ordering intuition.
Browser vs Node
Browsers and Node share the microtask idea but differ in phases and host APIs. If you interview for Node roles, also learn Node’s phases and nextTick. For frontend roles, rendering and requestAnimationFrame matter more.
Practice prompts
Predict output of mixed timeout/promise snippets, then explain why. HireReadyAI JavaScript mocks are useful for forcing verbal explanation, not only silent prediction.