Thursday, April 9, 2015

Improving Angular.js performance using One Time Binding

In the previous post I explained how the $digest loop works and how to increase performance using the ng-model-options directive. In this post we’ll take a look at ‘one time binding’ feature.

As I mentioned before the $digest loop goes through all the registered watches every time in order to check whether they need to be updated. However not all our scope variables and models should have binding or be updated after they have been initialized, for example: a logo path, a title, names, some constant options that we used ng-repeat for them and so on. All those variables should be initialized and not to be updated until a full page refresh.

One time binding is a feature that was introduced along with ng-model-options in Angular 1.3. In order to set that a scope variable should not be updated all you have to do is add :: before the variable name:

<input type="text" ng-model="name" value="text" />
{{::name}}
{{name}}


Adding it before the scope variable tells Angular not to register a watch on the variable and so decreases the amount of watches for the $digest loop to check which leads to increase in the app’s performance.

Enjoy

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