Edit in JSFiddle

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

app.controller('PersonCtrl', function () {
    this.startsWithW = function (item) {
        return /w/i.test(item.name.substring(0, 1));
    };
    this.friends = [{
        name: 'Andrew'        
    }, {
        name: 'Will'
    }, {
        name: 'Mark'
    }, {
        name: 'Alice'
    }, {
        name: 'Todd'
    }];
});

<div ng-app="app">
    <div ng-controller="PersonCtrl as person">
        <ul>
            <li ng-repeat="friend in person.friends | filter:person.startsWithW">
                {{ friend }}
            </li>
        </ul>
    </div>
</div>