JavaScript Animations in AngularJS Applications

Core points

• AngularJS is an excellent framework for building single-page web applications, and its animation support is one of its key features. JavaScript animations can be used to add animation effects to AngularJS applications. The difference between CSS and JavaScript animations is only in the way they are defined.
• Custom Angular JavaScript animations are defined in the animation method of the Angular module. The animation name begins with a dot. Each animation operation accepts two parameters: the object representing the current DOM element that will be applied to the animation, and the callback function called after the animation is completed.
• Animation can be applied to various AngularJS directives, such as ng-view, ng-repeat, ng-hide, and custom directives. For example, you can add animations in the ng-view directive to create visual effects when the user switches between views; or add animations in the ng-repeat directive to indicate visually when changes occur.
• Animation While it can make the application more vivid, overuse of animation can cause the application to slow down and can overwhelm the end user. Therefore, animation should be used optimized and strategically.

AngularJS is a feature-rich framework for creating single-page web applications that provide all the features you need to build rich and interactive applications. One of the key features of Angular is its support for animation.

We can animate part of the application to indicate changes that are occurring. In my last post, I introduced support for CSS animations in Angular applications. In this article, we will learn how to use JavaScript to add animations to AngularJS applications.

In Angular, the only difference between CSS and JavaScript animations is how they are defined. There is no difference in how defined animations are used. First, we need to load the ngAnimate module into the root module of the application.

angular.module('coursesApp', ['ngAnimate']);

The animation events to be processed in JavaScript animations also remain unchanged. The following is a list of commands that support animation and their events for different operations:

InstructionsEventsng-viewenter, leave ng-includeenter, leaveng-switchenter, leaveng-ifenter, leaveng-repeatenter, leave, moveng-showadd, removeng-hideadd, removeng-classadd, remove The above list is the same as the one in the previous post, but does not mention the corresponding CSS classes because we do not need them to define JavaScript animations. These events are generated only when the application module loads the ngAnimate module. Now let's see how to animate some directives.

Custom Angular Syntax

The basic framework of custom JavaScript animation is as follows:

angular.module('coursesApp', ['ngAnimate']);

When writing JavaScript animations in AngularJS, remember the following points:

1. The animation name begins with a dot (.).
2. Each animation operation accepts two parameters:
   • An object that is the current DOM element that will apply the animation. If jQuery is not loaded before AngularJS is loaded, it is a jQlite object; otherwise, it is a jQuery object.
   • The callback function called after the animation is completed. The operation of the instruction will be paused before calling the done function.

We have many JavaScript libraries such as jQuery, Greensock, Anima, etc., which simplify the work of writing animations. For simplicity, I'm using jQuery to create animations in this article. To learn about other libraries, you can visit their respective websites.

Add animated to ng-view

Animes are applied to the ng-view directive when the user switches between views of the AngularJS application. As shown in the table above, we can add animations when the view enters or leaves. There is no need to deal with both cases; we can add animations for situations that seem necessary.

The following animations will produce some visual effects when the view enters the page:

angular.module('coursesApp').animation('.name-of-animation', function(<injectables></injectables>) {
  return {
    event: function(elem, done){
      // 动画逻辑
      done();
    }
  };
});

The above code will create a sliding effect when the view enters the page. The done method is passed as a callback. This is to indicate that the animation is completed and the framework can now proceed to the next operation.

Please note how the animate() method is called. We don't have to convert elements to jQuery objects, because the jQuery library is loaded before AngularJS is loaded.

Now we need to apply this animation to the ng-view directive. Although the animation is defined in JavaScript, by convention we use classes on the target directive to apply it.

courseAppAnimations.animation('.view-slide-in', function () {
  return {
    enter: function(element, done) {
      element.css({
        opacity: 0.5,
        position: "relative",
        top: "10px",
        left: "20px"
      })
      .animate({
        top: 0,
        left: 0,
        opacity: 1
        }, 1000, done);
    }
  };
});

Add animated to ng-repeat

ng-repeat is one of the most important instructions, which provides many options. The two basic operations of this instruction are filtering and sorting. Depending on the type of operation performed, items under the instruction will be added, deleted, or moved.

Let's apply some basic animation so that the user can see when changes occur.

<div class="view-slide-in" ng-view=""></div>

Add animated to ng-hide

The

ng-hide directive adds or removes the ng-hide CSS class on the target element. To apply animations, we need to handle the situation where we add and delete CSS classes. The class name will be passed to the animation handler class. This allows us to check the class and take appropriate actions.

The following is an animation code example that fades out or fades into elements when the ng-hide directive is activated or deactivated:

courseAppAnimations.animation('.repeat-animation', function () {
  return {
    enter : function(element, done) {
      console.log("entering...");
      var width = element.width();
      element.css({
        position: 'relative',
        left: -10,
        opacity: 0
      });
      element.animate({
        left: 0,
        opacity: 1
      }, done);
    },
    leave : function(element, done) {
      element.css({
        position: 'relative',
        left: 0,
        opacity: 1
      });
      element.animate({
        left: -10,
        opacity: 0
      }, done);
    },
    move : function(element, done) {
      element.css({
        left: "2px",
        opacity: 0.5
      });
      element.animate({
        left: "0px",
        opacity: 1
      }, done);
    }
  };
});

Add animated custom commands

To add animations to custom directives, we need to use the $animate service. Although $animate is part of the AngularJS core framework, ngAnimate should be loaded to take advantage of the service.

With the same demo as in the previous post, we will display a page with a list of courses. We create a directive that displays the details of the course in a box, and after clicking the "View Statistics" link, the content of the box will change. Let's add an animation so that the user can see the transition.

When the transition occurs, we will add a CSS class, which we will delete after the animation is complete. Here is the code for this directive:

angular.module('coursesApp', ['ngAnimate']);

As you can see, we perform the action after the animation is complete. When checking directive elements in browser developer tools, we will see that the classes switching-active and switching-add are added and removed very quickly. We can define CSS transitions or customize JavaScript animations to see the animations that are happening. Here is an example CSS transition that can be used with the above directives (for brevity, vendor prefixes are omitted):

angular.module('coursesApp').animation('.name-of-animation', function(<injectables></injectables>) {
  return {
    event: function(elem, done){
      // 动画逻辑
      done();
    }
  };
});

Or, the following is a jQuery animation that can be used for the same instruction:

courseAppAnimations.animation('.view-slide-in', function () {
  return {
    enter: function(element, done) {
      element.css({
        opacity: 0.5,
        position: "relative",
        top: "10px",
        left: "20px"
      })
      .animate({
        top: 0,
        left: 0,
        opacity: 1
        }, 1000, done);
    }
  };
});

One of these animations can be applied to custom directives just like we apply animations to built-in directives.

<div class="view-slide-in" ng-view=""></div>

You can view the actual effects of all the above animations on the demo page.

Conclusion

Animation can make the application more vivid if used properly and functionally. As we can see, AngularJS supports CSS and JavaScript animations richly. You can choose one of these based on the team's situation.

However, heavy use of animation can cause the application to be slowed down and the application seems to be overdesigned for the end user. Therefore, this weapon must be used with caution and optimization.

FAQs about JavaScript animations in AngularJS applications (FAQ)

How to create basic animations in AngularJS?

Creating a basic animation in AngularJS involves several steps. First, you need to include the AngularJS animation library in your project. This can be achieved by adding a reference to the "angular-animate.js" file in the HTML file. Next, you need to inject the "ngAnimate" module into your AngularJS application. This can be achieved by adding "ngAnimate" as a dependency in the application module. After you have done this, you can create animations using the CSS class and the AngularJS directive. For example, you can use the "ng-enter" and "ng-leave" classes to animate an element when it enters or leaves the DOM.

What are the key components of AngularJS animation?

AngularJS animation mainly consists of two key components: CSS and JavaScript. CSS is used to define the style and transitions of animations, while JavaScript is used to control the time and order of animations. In AngularJS, animations are created by associating CSS classes with specific AngularJS directives such as "ng-repeat", "ng-switch", and "ng-view". These directives automatically add and delete associated CSS classes at the right time, allowing you to create complex animations with minimal JavaScript code.

How to control the time of animation in AngularJS?

CSS transitions and animations can be used to control the time of animations in AngularJS. By specifying the "transition-duration" or "animation-duration" attributes in the CSS class, you can control how long the animation lasts. Additionally, you can use the "transition-delay" or "animation-delay" attributes to control the start time of the animation. These properties can be specified in seconds (s) or milliseconds (ms).

Can I create animations in AngularJS using JavaScript?

Yes, you can create animations in AngularJS using JavaScript. While CSS is often used for simple animations, JavaScript can be used for more complex animations that require precise control over the timing and order of animations. In AngularJS, you can programmatically control animations using the "$animate" service. This service provides methods for adding, deleting, and querying CSS classes, allowing you to create complex animations using JavaScript.

How to animate elements when entering or leaving the DOM in AngularJS?

In AngularJS, you can use the "ng-enter" and "ng-leave" classes to animate an element when it enters or leaves the DOM. AngularJS automatically adds and removes these classes when elements enter or leave the DOM. By defining CSS transitions or animations for these classes, you can create animations that trigger when an element enters or leaves the DOM.

How to use AngularJS animation with "ng-repeat"?

You can use AngularJS animation with "ng-repeat" by associating the CSS class with the "ng-repeat" directive. When an item is added to or removed from the 'ng-repeat' list, AngularJS automatically adds and removes the associated CSS class, triggering the corresponding animation. For example, you can use the "ng-enter" and "ng-leave" classes to animate the project when it is added to or removed from a list.

Can I use AngularJS animation with "ng-switch"?

Yes, you can use AngularJS animation with "ng-switch". Similar to "ng-repeat", you can associate a CSS class with the "ng-switch" directive to create an animation. When the "ng-switch" condition changes, AngularJS automatically adds and deletes the associated CSS class, triggering the corresponding animation.

How to use AngularJS animation with "ng-view"?

You can use AngularJS animation with "ng-view" by associating the CSS class with the "ng-view" directive. When the view changes, AngularJS automatically adds and deletes the associated CSS class, triggering the corresponding animation. This can be used to create page transition animations in AngularJS applications.

Can I use AngularJS animations with custom directives?

Yes, you can use AngularJS animations with custom directives. By using the "$animate" service in the link function of the directive, you can programmatically add, delete, and query CSS classes to create complex animations using JavaScript.

How to debug AngularJS animation?

You can use browser developer tools to debug AngularJS animations. By checking the animation elements in the DOM, you can see which CSS classes AngularJS is adding and removing. Additionally, you can enable or disable animation using the "enabled" method of the "$animate" service, which is very useful for debugging.

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