AngularJS Example:

Angular Radio Form

by dmitri14

HTML

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.9/angular.min.js"></script>
<form ng-controller="JimController as vm">
  Is Jim Lynch cool?
  <br>
  <label>
    <input type="radio" ng-model="vm.isJimCool" value="ofCourse" checked="checked"> Of Course!
  </label>
  <br>
  <label>
    <input type="radio" ng-model="vm.isJimCool" value="certainly"> Certainly!
  </label>
  <br>
  <label>
    <input type="radio" ng-model="vm.isJimCool" value="no"> I don't believe so.
  </label>
  <br>
  <br>
  <div class="jimerrormessage" ng-if="vm.displayError()">
    <br> Do you really think that? :'(
    <br>
    <br>
  </div>
</form>

CSS

.jimerrormessage {
  font-size: 20px;
  color: red;
  border: 3px solid red;
  border-radius: 60%;
  text-align: center;
}

JavaScript

angular.module('JimApp', [])
  .controller('JimController', JimController);

function JimController() {
  var vm = this;
  vm.isJimCool = "ofCourse";
  vm.displayError = function displayError() {
    return vm.isJimCool === 'no';
  };
}