Попробуйте следующее:
angular.module("test", []).filter("purger", function() {
return function(input) {
return input.replace(/[^\w\s]/gi, "");
}
}).controller("testController", function($scope, purgerFilter) {
$scope.value = purgerFilter("^..test/$");
$scope.onChange = function() {
$scope.value = purgerFilter($scope.value);
}
})
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
<body ng-app="test" ng-controller="testController">
<textarea type="text" ng-model="value" ng-change="onChange()" row=2></textarea>
</body>