您忘记加载所选库：

wp_register_script( \'js_chosen\', \'https://raw.github.com/harvesthq/chosen/master/chosen/chosen.jquery.js\', array(\'jquery\') );
wp_register_script( \'js_custom\', plugin_dir_url( __FILE__ ) . \'js/jquery.js\', array(\'jquery\', \'js_chosen\') );
wp_enqueue_script ( \'js_custom\' );

这已经很老了，但对于其他阅读此问题的人来说，不要使用github，因为它不起作用。

<?php

/**
 * Plugin Name: Add JQuery Chosen Quickly
 * Plugin URI: http://wordpress.stackexchange.com/questions/85824/
 * Description: Test/Add chosen to site without adding any files
 * Version: 1.0
 */

function enqueue_chosen_jquery() {
    wp_register_style( \'chosencss\', \'https://cdnjs.cloudflare.com/ajax/libs/chosen/1.1.0/chosen.min.css\', false, \'1.1.0\', \'all\' );
    wp_register_script( \'chosenjs\', \'https://cdnjs.cloudflare.com/ajax/libs/chosen/1.1.0/chosen.jquery.min.js\', array( \'jquery\' ), \'1.1.0\', true );
    wp_enqueue_style( \'chosencss\' );
    wp_enqueue_script( \'chosenjs\' );
    }
add_action( \'wp_enqueue_scripts\', \'enqueue_chosen_jquery\' );

// Assuming jQuery is loaded in the head
function chosen_jquery_inline() {
if ( wp_script_is( \'jquery\', \'done\' ) ) { ?>
    <script type="text/javascript">
    jQuery(document).ready(function ($) {
        $( ".chzn-select" ).chosen();
    });
    </script>
<?php }
add_action( \'wp_head\', \'chosen_jquery_inline\', 999 );