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Looking good and informative, but to be honest I am really interested in use cases. I think I understand how to use generators but I have no idea where I could

by ponyous 11y ago

Looking good and informative, but to be honest I am really interested in use cases. I think I understand how to use generators but I have no idea where I could use them in real-world scenarios. Same goes for WeakMaps, Proxies... Anyone care to give some examples?

heifer2822 11y ago
checkout Koa to see a great use case of generators. By yielding to asychronous code (instead of callbacks) you can write JS that looks like it's synchronous.
- NikolaeVarius 11y ago
  What is the advantage of using generators versus promises?
  - callahad 11y ago
    In this case, Koa uses generators and promises together to emulate the behavior of async/await style concurrency. You can see how Babel 5.x transforms ES7 async/await into generators and promises at https://github.com/babel/babel/blob/v5.8.34/packages/babel/src/transformation/templates/helper-async-to-generator.js https://github.com/babel/babel/blob/v5.8.34/packages/babel/s...
  - chowes 11y ago
    http://stackoverflow.com/a/28032438 http://stackoverflow.com/a/28032438 gives a great overview to the pros and cons of both approaches.
chowes 11y ago
Check out http://jlongster.com/A-Study-on-Solving-Callbacks-with-JavaScript-Generators http://jlongster.com/A-Study-on-Solving-Callbacks-with-JavaS... and the follow up post. It's easy enough to start using generators alongside your existing async solution (callbacks or promises). Proxies can be used for data-binding, similar to Object.observe. I've also yet to find a case where I need WeakMaps instead of an Object or Map. All the benefits seem to be a bit too theoretical, but I likely haven't dug into it hard enough.
- danielnaab 11y ago
  I've used a WeakMap for a kind of memoization. Assume an immutable object may undergo an expensive transform that returns an object, which is then stored in a WeakMap keyed to the immutable. When there are no new references to that object, the garbage collector will clean it up, but otherwise the expensive transform may be avoided with a lookup on the WeakMap. It provides a pretty nice way to decouple your caching from the rest of the codebase.
slasaus 11y ago
I'm currently using Proxy to transparently version data that is saved in an IndexedDB.
_greim_ 11y ago
Too many use cases to list, but generally a nice way to for...of anything, for example a recursive binary tree traversal: [Symbol.iterator]() { if (this.left) { yield* this.left[Symbol.iterator](); } yield this.value; if (this.right) { yield* this.rightSymbol.iterator](); } } ... for (const value of myTree) { ... }

by ponyous 11y ago

heifer2822 11y ago

checkout Koa to see a great use case of generators. By yielding to asychronous code (instead of callbacks) you can write JS that looks like it's synchronous.

NikolaeVarius 11y ago
What is the advantage of using generators versus promises?
- callahad 11y ago
  In this case, Koa uses generators and promises together to emulate the behavior of async/await style concurrency. You can see how Babel 5.x transforms ES7 async/await into generators and promises at https://github.com/babel/babel/blob/v5.8.34/packages/babel/src/transformation/templates/helper-async-to-generator.js https://github.com/babel/babel/blob/v5.8.34/packages/babel/s...
- chowes 11y ago
  http://stackoverflow.com/a/28032438 http://stackoverflow.com/a/28032438 gives a great overview to the pros and cons of both approaches.

chowes 11y ago

Check out http://jlongster.com/A-Study-on-Solving-Callbacks-with-JavaScript-Generators http://jlongster.com/A-Study-on-Solving-Callbacks-with-JavaS... and the follow up post. It's easy enough to start using generators alongside your existing async solution (callbacks or promises). Proxies can be used for data-binding, similar to Object.observe. I've also yet to find a case where I need WeakMaps instead of an Object or Map. All the benefits seem to be a bit too theoretical, but I likely haven't dug into it hard enough.

danielnaab 11y ago
I've used a WeakMap for a kind of memoization. Assume an immutable object may undergo an expensive transform that returns an object, which is then stored in a WeakMap keyed to the immutable. When there are no new references to that object, the garbage collector will clean it up, but otherwise the expensive transform may be avoided with a lookup on the WeakMap. It provides a pretty nice way to decouple your caching from the rest of the codebase.

slasaus 11y ago

I'm currently using Proxy to transparently version data that is saved in an IndexedDB.

_greim_ 11y ago

Too many use cases to list, but generally a nice way to for...of anything, for example a recursive binary tree traversal: [Symbol.iterator]() { if (this.left) { yield* this.left[Symbol.iterator](); } yield this.value; if (this.right) { yield* this.rightSymbol.iterator](); } } ... for (const value of myTree) { ... }