AngularJS – 6 Tips to Optimize the Digest Cycle

This article represents tips on making optimal usage of digest cycle which slowers the Angular app. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

Following are the key points in relation with optimization of Digest cycle:

• Only the most critical variables should be watched. For instance, one should avoid using $digest method in loop for every message exchanged. • Usage of one-time binding syntax to avoid objects being added to $$watchers list and thus being checked for updates with each digest run. The syntax looks like {{::name}}. With this syntax, once the name variable is resolved, Angular removes the name property from the$$watchers list. • Usage of$scope.$apply vis-a-vis$scope.$digest: When$scope.$apply API is called, it triggers the whole app in the$digest loop which in trun runs $Scope.$digest(). This, in turn, traverses all scopes and bindings of the app looking for the change. One may, thus, want to use $scope.$digest in the local scope object if one is aware of the changes vis-a-vis scope.
• Computations in $watch should be made as minimal as method. • Optimal usage of ng-repeat as it increases number of $$watchers. The thumb rule is that more$$watchers there are, more slower the app gets. • One should consider setting the third parameter in$timeout function to false to skip the $digest loop when no watched variables are impacted by the invocation of the$timeout callback function.