jQuery Plupload restrict number of uploads

I have been working on this code for some time now trying to get it to work properly. I want to restrict the use from uploading more that 2 images in total.

The line var upa = $('.uploader').plupload('getUploader'); it giving an error of Uncaught TypeError: Object [object Object] has no method 'plupload'

    var maxfiles=2;
    $('.uploader').each(function(){
        var $uploader = $(this);
        $uploader.pluploadQueue($.extend({
            runtimes: 'html5,flash,html4',
            url : '../admin/extras/upload.php',
            max_file_size : '2mb',
            chunk_size : '2mb',
            unique_names : true,                
            filters : [
                {title : "Image files", extensions : "jpg"}
            ],
            resize : {width : 800, height : 600, quality : 90},
            flash_swf_url : 'js/mylibs/forms/uploader/plupload.flash.swf',
            init : {
                FilesAdded: function(up, files) {
                    plupload.each(files, function(file) {
                        if (up.files.length > maxfiles) {
                            up.removeFile(file);
                        }
                        var upa = $('.uploader').plupload('getUploader');
                        var i = 0;
                        while (i<=upa.files.length) {
                            ultimo = upa.files.length;
                            if (ultimo > 1) {
                                if (i > 0) {
                                    ultimo2 = ultimo - 1;
                                    ii = i-1;
                                    if (ultimo2 != ii) {
                                        if (up.files[ultimo - 1].name == upa.files[i-1].name) {
                                            up.removeFile(file);
                                        }
                                    }
                                }
                            }