What are some ways to improve the performance of an AngularJS application?

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ICSM Computer · Answer

Improving the performance of an AngularJS application involves optimizing various aspects such as data binding, digest cycle efficiency, lazy loading, and reducing unnecessary computations. Here are some key strategies:

1. Optimize Digest Cycle

Use ng-if instead of ng-show/ng-hide
1. ng-if removes the element from the DOM, while ng-show just hides it, reducing the number of watchers.
Minimize ng-repeat usage
1. Use one-time binding (::) for static data.
2. Use track by to improve performance:
  <div ng-repeat="item in items track by item.id">
Consider pagination or infinite scrolling to reduce large lists.

2. Reduce Watchers & Bindings

Use one-time binding (::) for data that doesn’t change:
Remove unnecessary $watch expressions.
<h1>{{ ::title }}</h1>
Use debouncing or throttling for events like keyup or scroll using lodash or $timeout.

3. Lazy Loading & Minification

Lazy load Angular modules using ocLazyLoad or ui-router’s resolve.
Minify and concatenate JavaScript and CSS files to reduce HTTP requests.

4. Optimize Filters & Expressions

Avoid using filters inside ng-repeat as they create a new function call in each digest cycle:
<div ng-repeat="user in users | filter:searchText">
Instead, use pre-filtering in the controller:
$scope.filteredUsers = $filter('filter')($scope.users, $scope.searchText);
Use limitTo instead of filter inside ng-repeat where possible.

5. Optimize API Calls

Use $cacheFactory or localStorage to store API responses.
Debounce API calls when typing in a search input.
Use resolve in ui-router to fetch data before rendering a view.

6. Use `bindOnce` for Directives

In custom directives, avoid scope: {} for static data.
Use bindToController: true for better performance.

7. Avoid Deep Watches

$scope.$watch with deep watching (true as the third argument) slows down performance. Avoid it if possible:

$scope.$watch('largeObject', function(newVal, oldVal) {
    // Avoid deep watch if not necessary
}, true);

8. Optimize DOM Manipulations

Use directives instead of controllers to manipulate the DOM.

Use $timeout or $applyAsync to batch updates and reduce digest cycles.

9. Reduce Dependencies

Remove unnecessary third-party libraries.

Use AngularJS' built-in services instead of external ones if possible.

10. Enable Production Mode

Use ng-strict-di to catch dependency injection issues in production.

Minify and use AngularJS in production mode (angular.min.js).

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What are some ways to improve the performance of an AngularJS application?

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1 Answers

1. Optimize Digest Cycle

2. Reduce Watchers & Bindings

3. Lazy Loading & Minification

4. Optimize Filters & Expressions

5. Optimize API Calls

6. Use bindOnce for Directives

7. Avoid Deep Watches

8. Optimize DOM Manipulations

9. Reduce Dependencies

10. Enable Production Mode

6. Use `bindOnce` for Directives