我有一个自定义字段（我使用高级自定义字段插件）设置为在创建新帖子时显示。用户必须输入4位数的年份。不超过4个字符，不少于。我的职能如下。php代码：

function make_year_created_equal_4_chars_init(){
  wp_enqueue_script(\'jquery\');
}
function make_year_created_equal_4_chars() {
  echo "<script type=\'text/javascript\'>\\n";
  echo "
      jQuery(\'#acf-field-artwork_created\').blur(function() {
      selected = jQuery(\'#acf-field-artwork_created\').length;
        if (selected != 4) {
            alert( \'A 4 digit year must be entered in the Artwork Created field\' );
        }
    });
";
echo "</script>\\n"; 
}
add_action(\'admin_init\', \'make_year_created_equal_4_chars_init\');
add_action(\'edit_form_advanced\', \'make_year_created_equal_4_chars\');
add_action(\'edit_page_form\', \'make_year_created_equal_4_chars\');

这是我的标记：

<input type="text" id="acf-field-artwork_created" class="text" name="fields[field_52e10c7db579e]" placeholder="" />

除一个方面外，这一切都很好。我没有报告JS错误，如果输入的字符少于4个或多于4个，那么一旦我离开字段（onblur），就会触发错误警报。

我的问题是，即使我使用4个字符，它仍然会触发。

感谢您的帮助。

function make_year_created_equal_4_chars() {
?>
<script type=\'text/javascript\'>
    // This is a shorthand for "jQuery(document).ready()"
    jQuery(function($) { 
        $(\'#acf-field-artwork_created\').blur(function() {
            // Please notice the declaration of \'selected_length\'.
            // It is important to declare it with \'var\' so that
            // you don\'t end up with it in the global scope.
            var selected_length = $(this).val().length;

            if (selected_length != 4) {
                alert( \'A 4 digit year must be entered in the Artwork Created field\' );
            }
        });
    });
</script>
<?php
}