Hacker News new | ask | show | jobs
by qwertyuiop924 3603 days ago
Two-way binding CAN be fast, however, due to various issues, Angular's only option was Dirty Checking, which is sloooow.

And no, a depgraph doesn't make it fast. What can make it fast is firing less events, using better triggers, and basically handling it exactly the way that Angular didn't.

VDOM can help, but really not much. However you want to put it, two-way binding is costly, and it should be avoided whenever possible, or minimized by catching multiple bind events at a higher up element on the tree (see http://lhorie.github.io/mithril-blog/asymmetrical-data-bindi...)

Just spraying it everywhere, the way Angular encourages, with no optimization (like the aforementioned asymetrical bindings), should be considered an antipattern.
2 comments
saskurambo 3603 days ago
Data binding is also about computates function where you know the dependencies of this and know when recalculate it
link
qwertyuiop924 3603 days ago
Are you talking about Computed Values? Because Data Binding has nothing to do with that. Not really.

In any case, Computed values make 2 way binding more expensive, because you have to run a depgraph on all the vars that are part of the binding network, every time an event fires. This is O(n). This is only one reason why Computed Values, as implemented in JS, are a Bad Idea. If you have to update a var on event fire, okay, but leaving the things everywhere is slow and ungainly. If you instead change the var to a function call, you can optimize far better, because you only have to update when the value is read.

In conclusion, if you want to polymorphism between functions and variables, treat everything as a function, not as a variable.

At least, I think that's a response to your question. Your English is pretty broken, so it's hard to tell. Sorry.

link
saskurambo 3603 days ago
Angular 2way is based on dirty check. Ractive and vue.js are really data binding with atomic changes.
link
qwertyuiop924 3603 days ago
I said nothing about Ractive and Vue. Their 2 way binding is better, but with large quantities of bindings, it's still slow.
link
saskurambo 3603 days ago
Virtual dom consume more computation processor while data binding consume more memory.
link
qwertyuiop924 3603 days ago
...In theory, but IIRC, binding doesn't cover all the types of updates that vdom does, and vdom is better at avoiding thrashing.
link