How can I pass a parameter to a setTimeout() callback?

I am getting "t is not defined" error when trying to execute the following code:

TaskList.prototype.GetTaskItems = function() {

var t = this;
%$.ajax({

...,
success: function(data) {...},
error: function() {

setTimeout("t.GetTaskItems()", 30000);

}

});

}

Not too sure why it doesn't work, but here's a workaround:

setTimeout(function() {

t.GetTaskItems();

, 30000);