autosaving post meta

admin.js

jQuery('button').on('click', function(){
  ...
  wp.autosave.server.triggerSave();
  ...
})

admin.php

<?php
function print_switch_mode_button() {
  ...
  ?>

  <span class="hidden">
    <input id="lorem" name="_nama_post_meta" type="hidden"  value="<?php echo $current_value; ?>">
    <?php wp_nonce_field( basename(__FILE__), '_nama_post_meta_nonce' ); ?>
  </span>

  <?php
  ...
}
add_action( 'media_buttons', 'print_switch_mode_button', 999);


function save_post_meta( $post_id ) {
  if ( ! isset( $_POST['_nama_post_meta_nonce'] ) || ! wp_verify_nonce( $_POST['_nama_post_meta_nonce'], basename(__FILE__) ) ){
    return;
  }

  if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
    return;
  }

  if( empty( $_POST ) ) {
    return;
  }

  if( ! isset( $_POST['_nama_post_meta'] ) )
    $_POST['_nama_post_meta'] = '';

  update_post_meta( $post_id , $_POST['_nama_post_meta']);
}
add_action( 'save_post', 'save_post_meta' );