AngularJS Example:

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<div ng-app>
  <div ng-controller="TodoCtrl">
    
    <div class="fab" ng-class="{'open': fabOpen}" ng-click="toggleFab()">
      <span ng-show="!fabOpen">FAB</span>
      <h4 ng-show="fabOpen">Just a test</h4>
    </div>
    
  </div>
</div>

SCSS

$time: 400ms;
.fab {
  -webkit-transition-duration: 	$time;
	-moz-transition-duration: 		$time;
	-o-transition-duration: 		$time;
  transition-duration: 			$time;
    
  border-radius:50%;
  background:#358FE8;
  display:inline-block;
  height:80px;
  line-height:80px;
  width:80px;
  position:fixed;
  bottom:16px;
  right:16px;
  text-align:center;
  cursor:pointer;
  color:white;
  &.open {
    background:#fff;
    color:black;
    border:1px solid #eee;
    border-radius:2px;
    
    left: 16px;
    width:auto;
    height:90%;
  }
}

JavaScript

function TodoCtrl($scope) {
	$scope.fabOpen = false;
  $scope.toggleFab = function() {
  	$scope.fabOpen = !$scope.fabOpen;
  }
}