demo.html

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
</head>
<body>

    <div ng-app="app" ng-controller="demoCtrl">
        <p ng-bind-html="testString | nl2br"></p>
        <p ng-bind-html="undefinedString | nl2br"></p>
    </div>

    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.5/angular.min.js"></script>
    <script src="index.js"></script>
    <script>
        angular.module('app', ['nl2br-filter'])
        .controller('demoCtrl', function ($scope) {
            $scope.testString = `Text
                                 with newlines.

                                 And <b>HTML</b> that should become escaped.`;
        });
    </script>

</body>
</html>