how to use jquery in wordpress code example

Example 1: jquery wordpress starter code

jQuery(document).ready(function( $ ) {
  //Place your jQuery code here...
});

Example 2: wordpress use jquery in plugin

wp_register_script( 'my_plugin_script', plugins_url('/my_plugin.js', __FILE__), array('jquery'));
wp_enqueue_script( 'my_plugin_script' );