Filter

input.html

<input type="text" ng-model="letter">
<ul>
  <li ng-repeat="friend in person.friends | startsWithLetter:letter">
    {{ friend }}
  </li>
</ul>

Web\Javascript\AngularJS\filter.js

http://toddmotto.com/everything-about-custom-filters-in-angular-js/

app.filter('startsWithLetter', function () {
  return function (items, letter) {
    var filtered = [];
    var letterMatch = new RegExp(letter, 'i');
    for (var i = 0; i < items.length; i++) {
      var item = items[i];
      if (letterMatch.test(item.name.substring(0, 1))) {
        filtered.push(item);
      }
    }
    return filtered;
  };
});