use strict compliant version + handle undefined case

angular.filters.nl2br.js

/*

# Usage in html template:

"xxx | nl2br"

<div ng-bind-html=" YourString | nl2br "></div>

or:

"xxx | nl2br:Boolean"

Boolean( true or flase or just keep null) means is xhtml  or not

if is xhtml, replace with <br/> ; if not , replace with <br>

<div ng-bind-html=" YourString | nl2br:true "></div>


-------------------------

# Example:

//==Analog data===
$scope.items = [
    {"message": "test"},
    {"message": "New\nLine"},
]
//=====
<div class="comment" ng-repeat="item in items">
    <p ng-bind-html=" item.message | nl2br "></p>
</div>

-------------------------

# Output result:

<div class="comment ng-scope" ng-repeat="item in items">
    <p class="ng-binding" ng-bind-html=" item.message | nl2br ">
        test
    </p>
</div>
<div class="comment ng-scope" ng-repeat="item in items">
    <p class="ng-binding" ng-bind-html=" item.message | nl2br ">
        New<br>Line
    </p>
</div>

*/


'use strict';

angular.module('myApp')
  .filter('nl2br', function($sce){
    return function(msg,isXhtml) {
      if (!angular.isString(msg)) {
        return '';
      } else {
        isXhtml   = isXhtml || true;
        msg       = (msg + '').replace(/([^>\r\n]?)(\r\n|\n\r|\r|\n)/g, '$1'+ (isXhtml ? '<br />' : '<br>') +'$2');

        return $sce.trustAsHtml(msg);
      }
    };
  });

Nice solution, works perfect