70 exercises with solutions and explanations.
Before you start
1. We believe that a learning environment should be as realistic as possible. There are no Paste-n-Run sandboxes for coding tasks at Paqmind. You should use your own editor to write code and your own machine to run it – like a real programmer does.
2. Make sure you know the required theory, at least in the first approximation. Terms from the Curriculum should sound familiar for you. Refer to the Theory list below and always search for more. Start tomorrow (or next week) but start prepared.
3. Don't expect to pass the tutorial in one sitting. It's not a usual Easy-Level stuff made to massage your ego. We tried to make each exercise challenging, sometimes even discomfortable, yet enlightening. If you're here just to verify your knowledge, it may take a few days. But if you're new to the topic – it may easily take two weeks or more.
Refer to the How-to page for more information.
From the author
Sorry, couldn't resist a classic meme:
Let us clarify a few things. Take Promises, for example. You can see them as a set of async helpers that cover most everyday cases. Once a month you may get a special one where errors have to be handled differently, requests have to be arranged unusually, etc. Which will paralize you. You'll spend hours searching StackOverflow, asking random people for instant help, feeling humiliated. Or otherwise, in case you managed to finish this tutorial, you'll spend 10 minutes, writing your own special helper, without even seeing "the problem".
In this tutorial we deliberately decided to avoid "real" APIs like Node's FS or Browser's
Fetch in favor of "abstract"
setTimeout / setInterval-based code.
There are three decisive reasons for this.
1. The best learning model is to learn "one thing at a time". Learning an API and learning its underlying concepts are two different tasks. Learning how to combine those concepts together and apply them to solve a real-world problem is a third task.
2. Real APIs are almost always saturated with extra "noise". For example,
fetch will require you to
always apply two promise calls in a row, so you may take it as a norm (which it isn't).
FS.readFile will require you to learn buffers, to think about filesystem specifics. Again, basically,
you have to switch from the original intent of "learning some async" to learning stuff that slows
you down and may even be irrelevant (assuming so many possible JS application fields).
3. Timeouts and intervals aren't only extremely important on themselves, they are perfect as stubs for actual file, db, network, whatever "real" APIs. You'll also find them absolutely indispensable in tests, library code and many other key places. You can't overpractise them.