search form with ajax

Hello,
I am trying to develop a search tool for my plugin using ajax. I would like that by filling in the “user” field it returns the ID corresponding to this data (user_login).
Here is my PHP code:

$content= "Recherche";
   wp_enqueue_script( 'jb_script-js', plugins_url( 'js/jb_script.js', __FILE__ ),array('jquery'));

    // Pass ajax_url to script.js
    wp_localize_script( 'jb_script-js', 'plugin_ajax_object',
    array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );
	
$content.= '
<form id="search-form">
  <label for="user_login">Rechercher utilisateur :</label>
  <input type="text" id="user_login" name="user_login">
  <input type="button" value="Rechercher" onclick="searchUser()">
</form>
<div id="search-results"></div>
';

add_action( 'wp_ajax_search_user', 'search_user' );
add_action( 'wp_ajax_nopriv_search_user', 'search_user' );

function search_user() {
    global $wpdb;

    $user_login = $_POST['user_login'];
    $results = $wpdb->get_results( $wpdb->prepare( "SELECT ID FROM $wpdb->users WHERE user_login = %s", $user_login ) );

    echo json_encode($results);
    wp_die();
}

and here is my javascript code:

function searchUser() {
    var user_login = jQuery('#user_login').val();
    jQuery.ajax({
        type: 'POST',
        url: plugin_ajax_object.ajax_url,
        data: {
            'action': 'search_user',
            'user_login': user_login
        },
        success: function(results) {
            var output = "";
            for (var i = 0; i < results.length; i++) {
                output += "ID utilisateur : " + results[i].ID + "<br>";
            }
            jQuery('#search-results').html(output);
        }
    });
}

at the moment it doesn’t work. Where is the error?