How to change button's class when you change slide? - css

Question

I have an ionic slide box with 4 slides. You can switch between slides by clicking buttons on the bottom of the screen or you can simply scroll with your finger. Class 'active' needs to be added to the button when it's corresponding slide is active.
For example, if the second slide is active I want second button to have class 'active'. When you move to third slide (either by clicking third button or by sliding the screen), class 'active' is removed from second button and added to third button.
Classes now change when you click on a button but not when you scroll between slides. How do I fix this using AngularJS?
Link to Codepen: http://codepen.io/lu-kanemon/pen/doBNGz
Here is my code:
menu.html
<ion-view view-title="Menu">
<ion-content class="padding">
<ion-slide-box show-pager="false" on-slide-changed="slideHasChanged($index)">
<ion-slide>
<h1 class="slide-title"> Matches </h1>
</ion-slide>
<ion-slide>
<h1 class="slide-title"> Fitting jobs </h1>
</ion-slide>
<ion-slide>
<h1 class="slide-title"> Interesting events </h1>
</ion-slide>
<ion-slide>
<h1 class="slide-title"> Group conversations with open positions </h1>
</ion-slide>
</ion-slide-box>
</ion-content>
<div class="contacts-filters felix-filters button-bar">
<a class="button button-stable" ng-class="{active: selected=='m'}" ng-click="slide(0); selected='m'"><i class="fa fa-users"></i></a>
<a class="button button-stable" ng-class="{active: selected=='j'}" ng-click="slide(1); selected='j'"><i class="fa fa-suitcase"></i></a>
<a class="button button-stable" ng-class="{active: selected=='e'}" ng-click="slide(2); selected='e'"><i class="fa fa-map"></i></a>
<a class="button button-stable" ng-class="{active: selected=='c'}" ng-click="slide(3); selected='c'"><i class="fa fa-comments"></i></a>
</div>
</ion-view>
MenuCtrl.js
myApp
.controller('MenuCtrl', function($scope, $stateParams, $ionicSlideBoxDelegate){
//switch slides
$scope.slide = function(to) {
$scope.current = to;
$ionicSlideBoxDelegate.slide(to);
}
});

Answer 1

Just use addClass(className) and removeClass(className) functions
currentElement.removeClass('active');
nextActiveElement.addClass('active');
You can initialize a variable (current) with the first one (if there is at least one), then once the next active element is fired remove the class from current, then set the newest element to current. This repeats over and over!