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Result
HTML
JavaScript
CSS

<body ng-app="myApp" ng-init="newClass=false">
    
    <button ng-click="newClass=!newClass">Toggle Class</button>
	<div class="defaultClass" ng-class="{newClass:newClass}">Some Text</div>
    
</body>

var app = angular.module("myApp",[]);

div{ padding: 10px; color: #fff; }
.defaultClass{ background: #148fa1; }
.newClass { background: #2e7cb8; }