The customize_controls_print_scripts WordPress PHP action fires when Customizer control scripts are printed.
Usage
add_action('customize_controls_print_scripts', 'your_custom_function');
function your_custom_function() {
// your custom code here
}
Parameters
This action does not have any parameters.
More information
See WordPress Developer Resources: customize_controls_print_scripts
Examples
Enqueue a custom script for the theme customizer
This code enqueues a custom JavaScript file for the theme customizer screen.
add_action('customize_controls_print_scripts', 'enqueue_customizer_script');
function enqueue_customizer_script() {
    wp_enqueue_script('your-customizer-script', get_template_directory_uri() . '/js/customizer.js', array('jquery'), '1.0', true);
}
Add custom JavaScript to the theme customizer
This code adds custom JavaScript directly to the theme customizer screen.
add_action('customize_controls_print_scripts', 'add_customizer_inline_script');
function add_customizer_inline_script() {
    ?>
    <script type="text/javascript">
    jQuery(document).ready(function($) {
        // your custom jQuery code here
    });
    </script>
    <?php
}
Add CSS to the theme customizer
This code adds custom CSS to the theme customizer screen.
add_action('customize_controls_print_scripts', 'add_customizer_inline_css');
function add_customizer_inline_css() {
    ?>
    <style type="text/css">
        /* your custom CSS here */
    </style>
    <?php
}
Modify theme customizer controls
This code manipulates theme customizer controls using JavaScript.
add_action('customize_controls_print_scripts', 'modify_customizer_controls');
function modify_customizer_controls() {
    ?>
    <script type="text/javascript">
    jQuery(document).ready(function($) {
        // Hide a specific control
        $('li#customize-control-your-control-id').hide();
    });
    </script>
    <?php
}
Add custom HTML to the theme customizer
This code adds custom HTML to the theme customizer screen.
add_action('customize_controls_print_scripts', 'add_custom_html_to_customizer');
function add_custom_html_to_customizer() {
    ?>
    <div class="your-custom-html">
        <!-- your custom HTML content here -->
    </div>
    <?php
}