May 2018
Intermediate to advanced
376 pages
9h 22m
English
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Lesson 30. Promises
After reading lesson 30, you will be able to
- Use promise-based libraries to fetch asynchronous data
- Do basic error handling for promises
- Memoize asynchronous calls using Promise.resolve
- Combine several promises into one
A promise is an object that represents an eventual value. You can access this eventual or future value by calling .then() on the promise and supplying a callback function. The promise will eventually invoke this callback with the value. If the promise is still waiting for the value (the promise is in a pending state), then the promise will wait until the value is ready or has loaded (at which point the promise enters the resolved state) before invoking the callback with the value. If the promise has already ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.