if else statement in AngularJS templates
I want to do a condition in an AngularJS template. I fetch a video list from the Youtube API. Some of the videos are in 16:9 ratio and some are in 4:3 ratio.
I want to make a condition like this:
if video.yt$aspectRatio equals widescreen then
element's attr height="270px"
else
element's attr height="360px"
I'm iterating the videos using ng-repeat . Have no idea what should I do for this condition:
Angularjs (versions below 1.1.5) does not provide the if/else functionality . Following are a few options to consider for what you want to achieve:
( Jump to the update below (#5) if you are using version 1.1.5 or greater )
1. Ternary operator:
As suggested by @Kirk in the comments, the cleanest way of doing this would be to use a ternary operator as follows:
<span>{{isLarge ? 'video.large' : 'video.small'}}</span>
2. ng-switch directive:
can be used something like the following.
<div ng-switch on="video">
<div ng-switch-when="video.large">
<!-- code to render a large video block-->
</div>
<div ng-switch-default>
<!-- code to render the regular video block -->
</div>
</div>
3. ng-hide / ng-show directives
Alternatively, you might also use ng-show/ng-hide but using this will actually render both a large video and a small video element and then hide the one that meets the ng-hide condition and shows the one that meets ng-show condition. So on each page you'll actually be rendering two different elements.
4. Another option to consider is ng-class directive.
This can be used as follows.
<div ng-class="{large-video: video.large}">
<!-- video block goes here -->
</div>
The above basically will add a large-video css class to the div element if video.large is truthy.
UPDATE: Angular 1.1.5 introduced the ngIf directive
5. ng-if directive:
In the versions above 1.1.5 you can use the ng-if directive. This would remove the element if the expression provided returns false and re-inserts the element in the DOM if the expression returns true . Can be used as follows.
<div ng-if="video == video.large">
<!-- code to render a large video block-->
</div>
<div ng-if="video != video.large">
<!-- code to render the regular video block -->
</div>
In the latest version of Angular (as of 1.1.5), they have included a conditional directive called ngIf . It is different from ngShow and ngHide in that the elements aren't hidden, but not included in the DOM at all. They are very useful for components which are costly to create but aren't used:
<div ng-if="video == video.large">
<!-- code to render a large video block-->
</div>
<div ng-if="video != video.large">
<!-- code to render the regular video block -->
</div>
三元是做这件事最明显的方法。
<div>{{ConditionVar ? 'varIsTrue' : 'varIsFalse'}}</div>
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