Modified toJson method for AngularJs so Json.Net remains happy

gistfile1.js

$httpProvider.defaults.transformRequest = function (data) {
    function isWindow(obj) {
        return obj && obj.document && obj.location && obj.alert && obj.setInterval;
    }
    function isScope(obj) {
        return obj && obj.$evalAsync && obj.$watch;
    }
    function isFile(obj) {
        return toString.apply(obj) === '[object File]';
    }
    function toJsonWithJsonDotNetSupport(obj, pretty) {
        return JSON.stringify(obj, function (key, value) {
            var val = value;
            if(/^\$+/.test(key) && key !== "$type") {
                val = undefined;
            } else {
                if(isWindow(value)) {
                    val = '$WINDOW';
                } else {
                    if(value && document === value) {
                        val = '$DOCUMENT';
                    } else {
                        if(isScope(value)) {
                            val = '$SCOPE';
                        }
                    }
                }
            }
            return val;
        }, pretty ? '  ' : null);
    }
    return angular.isObject(data) && !isFile(data) ? toJsonWithJsonDotNetSupport(data, false) : data;
};