You can make AJAX requests to applications loaded from the SAME domain and SAME port.
Besides that, you should add dataType JSON
if you want the result to be deserialized automatically.
$.ajax({
url: "https://app.asana.com/-/api/0.1/workspaces/",
type: 'GET',
dataType: 'json', // added data type
success: function(res) {
console.log(res);
alert(res);
}
});