Angular Js service to get SharePoint Form Digest value (X-RequestDigest) value

GetSharePointFormDigestSvc.js

(function(){
	'use strict'
// Service that returns form digest value 
angular
.module('app')
.service('getFormDigestService', function($http, $q){
  
	//Define the service call
	this.getFormDigest = function(){
		//Fetch the Url	
		JSRequest.EnsureSetup();
		var appweburl = decodeURIComponent(JSRequest.QueryString['SPAppWebUrl']);
		//define promise
		var d = $q.defer();
		//Http post to the context info rest service
		$http.post(appweburl + "/_api/contextinfo", {
			data: '',
			headers: {
	        "Accept": "application/json;odata=verbose",
	        "Content-Type": "application/json;odata=verbose"
	        },
		}).success(function (data) {
		          //resolve the form digest to promise
			        d.resolve(data.d.GetContextWebInformation.FormDigestValue);
        }).error(function (err) {
			        d.reject("error finding form digest");
			        console.log("Error on retrieving digest value");
        });
		return d.promise;
	} 
});
	
})();