Are there performance benefits of one-way binding in Angular 1

Question

When reading about one-way binding in angular.component style, I came across multiple statements that < vs = produces less watchers (= will have additional watcher to propagate value change from child to parent).

However I've just created a dummy component, passed the object to it via = and < and number of watchers is the same.

So speaking strictly about performance: are there any diffirence between < and = ?

Answer 1

I came here with the same question, and was disappointed to see no answer... I have a small test application where I use all kinds of binding, three of them being one-way. I observed the number of watches (using ng-stats utility), got 42. I changed these "<" to "=", which changed the behavior of my app accordingly, of course. ng-stats still reported 42 watches.
So, at least in terms of watches, this brings no performance improvement.

I guess it is here more as a convenience, avoiding unwanted side effects (child changing a value, parent's value being changed unwillingly) and promoting good practices (using bound functions instead of watches, as explained below).

It can still be a way to avoid watches: a common practice when a parent wants to be advised of changes in a child it is to use two-way binding, set up a watch on the value, and react on changes.
An alternative is to set up a one-way binding (to feed the child), and to provide a callback (via a "&" binding), and thus to let the child to notify of changes via this callback.
It is more proactive and it removes a watch.