jQuery in WordPress

compatibility.js

/* Regular jQuery */
$('.hideable').on('click', function() {
  $(this).hide();
})

/* Compatibility Mode */
jQuery('.hideable').on('click', function() {
  jQuery(this).hide();
})

enqueue-backend.php

function my_admin_scripts() {
    wp_enqueue_script( 'my-great-script', plugin_dir_url( __FILE__ ) . '/js/my-great-script.js', array( 'jquery' ), '1.0.0', true );
}
add_action( 'admin_enqueue_scripts', 'my_admin_scripts' );

enqueue-theme.php

function my_theme_scripts() {
    wp_enqueue_script( 'my-great-script', get_template_directory_uri() . '/js/my-great-script.js', array( 'jquery' ), '1.0.0', true );
}
add_action( 'wp_enqueue_scripts', 'my_theme_scripts' );

using-dollar-footer.js

(function($) {
	
  $('.hideable').on('click', function() {
    $(this).hide();
  })
	
})( jQuery );

using-dollar-header.js

jQuery(document).ready(function( $ ) {
	
  $('.hideable').on('click', function() {
    $(this).hide();
  })
	
});