Lets say you have an array that is rendered in a ul
with an li
for each element and a property on the controller called selectedIndex
. What would be the best way to add a class to the li
with the index selectedIndex
in AngularJS?
I am currently duplicating (by hand) the li
code and adding the class to one of the li
tags and using ng-show
and ng-hide
to show only one li
per index.
If you don't want to put CSS class names into Controller like I do, here is an old trick that I use since pre-v1 days. We can write an expression that evaluates directly to a class name selected, no custom directives are necessary:
ng:class="{true:'selected', false:''}[$index==selectedIndex]"
Please note the old syntax with colon.
There is also a new better way of applying classes conditionally, like:
ng-class="{selected: $index==selectedIndex}"
Angular now supports expressions that return an object. Each property (name) of this object is now considered as a class name and is applied depending on its value.
However these ways are not functionally equal. Here is an example:
ng-class="{admin:'enabled', moderator:'disabled', '':'hidden'}[user.role]"
We could therefore reuse existing CSS classes by basically mapping a model property to a class name and at the same time keep CSS classes out of Controller code.