Edit in JSFiddle

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

myApp.filter('truncate', [function () {
    return function (text, length, end) {
        if (isNaN(length)) {
            length = 10;
        }

        if (end === void 0) {
            end = '...';
        }

        if (text.length <= length) {
            return text;
        }

        return text.substring(0, length - end.length) + end;
    };
}]);

<div ng-app="myApp">
    <p>{{ '1234567890' | truncate }}</p>
    <p>{{ '12345678901' | truncate }}</p>
    <p>{{ '1234567890' | truncate:4 }}</p>
    <p>{{ '1234567890' | truncate:3 }}</p>
    <p>{{ '1234567890' | truncate:2 }}</p>
    <p>{{ '12345678901' | truncate:10:'---' }}</p>
</div>