WordPress function to add the TinyMCE WYSIWYG editor to any custom field of type 'Textarea'

gistfile1.txt

// important: note the priority of 99, the js needs to be placed after tinymce loads
// important: note that this assumes you're using http://wordpress.org/extend/plugins/verve-meta-boxes/
// to create the textarea - otherwise change your selector

function admin_add_wysiwyg_custom_field_textarea()
{ ?>
<script type="text/javascript">/* <![CDATA[ */
	jQuery(function($){
		var i=1;
		$('.verve_meta_box_content textarea').each(function(e)
		{
		  var id = $(this).attr('id');
		  if (!id)
		  {
		   id = 'customEditor-' + i++;
		   $(this).attr('id',id);
		  }
		  tinyMCE.execCommand('mceAddControl', false, id);
		});
	});
/* ]]> */</script>
<?php }
add_action( 'admin_print_footer_scripts', 'admin_add_wysiwyg_custom_field_textarea', 99 );

where do we place this code?

same question, does this go into function?

this is really great - unfortunately the one thing my custom field really needs on the toolbar isn't there - unordered list formatting.
Any idea on how i might tailor the tool set?
PS yes - I needed tinyMCE.execCommand("mceAddEditor", false, id); in there so thanks @toitoit

for new visitors:
https://codex.wordpress.org/Function_Reference/wp_editor

You me stress

for new visitors:
https://codex.wordpress.org/Function_Reference/wp_editor

You me stress

save

when i use wp_editor in my widget / plugin it shows rich text but save button shows already saved and cant click

below code i use
` $content = 'Hello World!';
$editor_id = $this->get_field_id('text');

$settings = array(
    'media_buttons' => false,
    'textarea_rows' => 5,
    'teeny'         => true,
	'textarea_name' => $this->get_field_name('text'),
);

wp_editor( $content, $editor_id, $settings );`

anybody can help ?

This is my solution:

        $('textarea[name^="meta"]').each(function(i, e) {
            var id = !e.id ? 'customEditor-' + i : e.id;
            tinymce.init({
            selector: '#' + id,       
                setup: function (editor) {
                    editor.on('change', function ( e, i) {
                        tinymce.triggerSave();
                    });
                }
           });
        });