Question

This is the error function of $.ajax.
Why can’t I delay the call to $.ajax(this) ?

This works:

error: function (req, status, error) {
                    $.ajax(this);
                    return;
                }

But this doesn’t

error: function (req, status, error) {
                    var retry = function () { $.ajax(this); };
                    setTimeout(retry, 100);
                    return;
                }

Answer 1

Because the setTimeout callback runs in the context of the global object.
Therefore, this is window, not the AJAX settings.

You need to store this in a variable.