Time travel with javascript

Aka those weird behaviors when you try to squeeze asynchronous behaviors into a co-operative multi-tasking single-threaded execution model.

Transcript

1. Time traveling in Javascript Alex Dong August, 2013 Tuesday, August 6, 13
2. Weird Behaviors of Co-operative multi-tasking in Javascript Tuesday, August 6, 13
3. It started with a bug Tuesday, August 6, 13
4. WTF? Teleporting.js? The code can swim upstream or downstream against time. The concept of sequence in javascript could be trickier than one expects. Tuesday, August 6, 13
5. How javascript timer works? Timer delay in javascript is not guaranteed. All javascript in browser executes on a single threaded asynchronous events. When a new async event occurs, mouse click, XMLHttpRequest completion, will put it into a “waiting” queue. setTimeout(0, func) similar to ‘yield’ Tuesday, August 6, 13
6. We’re not done yet Enters “process.nextTick(fn)” in node.js It runs “before any other I/O events fire”. Much more efficient if you’re doing node.js Tuesday, August 6, 13
7. process.nextTick vs. setTimeout(0) Run Math.sqrt(i) for i in range(0, 1024*1024) Caution. This is what the doc says: It typically runs before any other I/O events fire, but there are some exceptions. Like what?! Tuesday, August 6, 13