JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.8/angular.min.js"></script>
<div ng-app="regApp" ng-controller="RegistrationCtrl" data-ng-init="GetEventDetail()">
     <h2>Registration for {{data.EventName}}</h2>
 <span class="btn" id="btnSave" ng-click="PostRegistration()">Save </span>

</div>

JavaScript

var app = angular.module('regApp', []);

app.controller('RegistrationCtrl', function ($scope, $http) {
    $scope.PostRegistration = function () {
        alert('click '); // <--- fires twice
        /// some code here -- 
    };
});