问题
I recently started studying about digest and performance improvements in AngulaJs and found on my website that I'm using tons of ng-if.
Sometimes in ng-if there is a variable that may change, but often is fixed at the startup of the controller and then never changes.
What should I do so to improve performance avoiding digest to evaluate every loop those unchangeable ng-if? Should I change directive? With what?
E.g
In my header template I have a div that can be seen only by particular type of user. It's just a div, so I don't want to call some different template.
I put <div ng-if="userIsSuperior()"> ... </div>
When first evaluated, the return vale of userIsSuperior() never changes (during this session of course), but I know that AngularJs Digest evaluates it every loop.
How can I avoid this? Or am I missing something?
回答1:
I think what you are looking for is one-time binding.
If you use:
<div ng-if="::userIsSuperior()"> ... </div>
Then the value of userIsSuperior() will only be calculated once and will stick to that value.
See demo.
回答2:
First answer solutions needs AngularJS > 2.
I found a valid solutions in using OnceJS, library for one-time-binding.
Here
来源：https://stackoverflow.com/questions/37559451/angularjs-alternative-to-ng-if-to-save-digest