Wordpress Right Way Using AJAX

functions.php

//In plugin or functions.php
add_action('wp_ajax_my_action_name',        'my_action_name');
add_action('wp_ajax_nopriv_my_action_name', 'my_action_name');

function my_action_name() {
  //
}

main.js

var data = {
    action  : 'my_action_name',
    whatever: ajax_object.we_value 
};