hackertube.io

What the heck is the event loop anyway? | Philip Roberts | JSConf EU

JSConf · talk · Watch on YouTube

Web developmentPython, Ruby & scripting languages

What it is

Philip Roberts explains the JavaScript event loop, call stack, callbacks and asynchronous behavior with live visualizations using a tool he built. It demystifies terms like non-blocking and single-threaded.

Why Hacker News recommends it

HN commenters repeatedly name it as the best explanation of the JS event loop and the first thing to watch before tackling async code.

  • 16 people recommended it
  • 14 different months
  • 5 strong recommendations
  • first 2015, last 2025

What HN commenters said

  1. “how async operations are scheduled on a single thread”

    Shows how async operations are scheduled on one thread.

    lollipop25, 2016-03 · Strong recommendation · in “Ask HN: How do I go about truly “understanding” JavaScript, or any language?”

  2. “Philip Roberts has a great lecture called what the heck is the event loop anyway?”

    Event loop understanding underpins async JS.

    zappo2938, 2016-10 · Strong recommendation · in “Understanding Async JavaScript”

  3. “The tool he created to display the event loop in real time is fantastic.”

    Event loop talk with a real-time visualization tool.

    keyvin, 2018-10 · Strong recommendation · in “Ask HN: What are some of the best technical talks you've heard?”

  4. “it's probably the most helpful deep-dive I've ever seen about some aspect of JavaScript”

    Deep-dive into JS event loop, key difference from Python.

    _bxg1, 2020-02 · Strong recommendation · in “Ask HN: How do I learn JavaScript?”

  5. “This one is my all time favorite”

    Favorite tech talk on the event loop.

    krisgenre, 2020-11 · Strong recommendation · in “How does the event loop work in JavaScript? [video]”

  6. “a great, very simple explanation.”

    Gives the mental model of the JS event loop.

    the_cat_kittles, 2015-03 · Recommendation · in “JavaScript Call Stack/Event Loop Visualization”

  7. “Listed among favorite tech talks.”

    hackaflocka, 2016-10 · Recommendation · in “Ask HN: What's your favorite tech talk?”

  8. “Be sure to understand the event loop.”

    Great talks on the event loop for beginners.

    mxschumacher, 2018-07 · Recommendation · in “Ask HN: What you wish you'd known before getting into JavaScript?”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: event loop, async javascript, call stack, callbacks, visualization

Also recommended by the same people