FileUpload allow Only Image Format Validate in JQuery

$('input:file').change(function () {

                var ext = this.value.split('.').pop();

                //   alert(ext);

                var FileExt = ['png', 'jpg','JPEG']

                if ($.inArray($(this).val().split('.').pop().toLowerCase(), FileExt) == -1) {

                    var xl = "Please Select image Files"

                    alert(xl);

                    this.$find('input:file').dispose();

                    return false;

                }

            });