Edit in JSFiddle

var myapp = angular.module('sampleapp', [ ]);

myapp.controller('samplecontoller', function ($scope) {

  
    $scope.loader = {
      loading: false,
    };
    
    $scope.showloader = function(){
        $scope.loader.loading = true ;
    }
    $scope.hideloader = function(){
        $scope.loader.loading = false ;
    }


});


 

<div ng-app="sampleapp">
<div ng-controller="samplecontoller">
    
    <div class="form">
        <p>Click to see the loader</p>
    <button class="btn btn-primary" ng-click="showloader()">Show loader</button>    
    <button class="btn btn-primary" ng-click="hideloader()">Hide loader</button>    
    
        
    
    </div>
    <div class="cancel">
        <button ng-show="loader.loading" class="btn btn-success">Loading...
        <i class="fa fa-spinner fa-spin"></i>
        </button>
        
    </div>
    
</div>
</div>

.form{
    padding:20px
}
.cancel{
    
    padding:20px;
}