From http://stackoverflow.com/questions/17559563/sending-ajax-post-jquery-in-rails-application

sample_ajax.js

$("someElement").ajaxSend(function(e, xhr, options) {
    var token = $("meta[name='csrf-token']").attr("content");
    xhr.setRequestHeader("X-CSRF-Token", token);
});
  		
$("someElement").click(function(){
    $.ajax(
      {
         type: "POST",
         url: "/products",
         beforeSend: function( xhr ) {
            xhr.overrideMimeType( "text/plain; charset=x-user-defined" );
            xhr.setRequestHeader("Accept", "text/javascript");
         },
         data: { product: { name: "Filip", description: "whatever" } },
         dataType: 'json', //xml, html, script, json
         success: doSomethingSuccess(dataServer),
         error: function( req, status, err ) {
            console.log( 'something went wrong', status, err );
        },
         complete: alert('Done!')
      });
});

function doSomethingSuccess(data){ }