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Async/await vs Coroutines vs Promises vs Callbacks
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callbacks related? Which one is better or worse? We are going to implement the same code with these 4 different approaches.
First of all, let’s define a simple
delay function, that resolves with a given value after a given amount of time elapsed.
This is the most recent feature of all 4 approaches.
- Clean code, low syntax noise
- Native in current Chrome, Node.js
- Still needs to be transpiled with Babel for most projects
Async Code With Promise Chaining
This is more oldschool than
- No extra libraries needed since Promises are native
- Noisy callbacks
Async Code With Callbacks
Years ago this was the usual way to handle async continuations.
- Easy to understand
- No libs needed, backward compatible
- Pyramid of doom
- More difficult to maintain
Async Code With Coroutines
This is the most exotic one, having similar syntax to
- No pyramid of doom
- Flow can be traced easily
- Some coroutine library is needed
- Generators must be used
If you are curious how a simple coroutine runner works, here we go. It’s just a simplified implementation to have an understanding of the concept.
Conclusions & Opinions
In most cases
async/await is the best choice, since it makes the code maintainable and it’s supported by Node.js and modern browsers. Older browsers or Node.js versions can be targeted by Babel transpiler.
Some folks like to write callback hells and pyramid of dooms. It’s time for them to move on and practise coding with
Of course, without a deep knowledge of Promises,
async/await or coroutines are just magic, so it is very valuable to have a close friendship with Promises.
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