AngularJS Example:

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<div ng-app>
  <div ng-controller="TodoCtrl">
   <div ng-repeat-start="char in uniqChar | orderBy: 'char'">
          <button ng-repeat="letter in alphabet" href="" ng-disabled="char !=letter">
              {{letter | uppercase}}
            </a>
      </div>
      <div ng-repeat-end=""></div>
  </div>
</div>

JavaScript

function TodoCtrl($scope) {
  $scope.alphabet = "abcdefghijklmnopqrstuvwxyz".split("");

      $scope.uniqChar = ['a', 'g', 'm'];

}