The simple answer: Don’t bother with the Admin AJAX API, use the REST API!
Tell WordPress about your endpoint:
add_action( 'rest_api_init', function () { // register dongsan/v1/whatever
register_rest_route( 'dongsan/v1', '/whatever/', array(
'methods' => 'POST', // use POST to call it
'callback' => 'dongsan_whatever' // call this function
) );
} );
Now we have an endpoint at example.com/wp-json/dongsan/v1/whatever!
We told WordPress to run dongsan_whatever when it gets called, so lets do that:
function dongsan_whatever( \WP_REST_Request $request ) {
$name = $request['name'];
return 'hello '.$name;
}
Note that we used $request['name'] to get a name parameter!
So we have a URL:
example.com/wp-json/dongsan/v1/whatever
And we can send a POST request with a name to it and get some JSON back that says Hello ‘name’! So how do we do that?
Simples, it’s a standard jQuery post request:
jQuery.post(
'https://example.com/wp-json/dongsan/v1/whatever',
{ 'name': 'Dongsan' }
).done( function( data ) {
Console.log( data ); // most likely "Hello Dongsan"
} );
Further reading: