This solution actually gets the textbox to behave as per the 'maxlength' standards (not allowing to key-in more characters)
$('#first-name').textbox();
$('#first-name').textbox('textbox').attr('maxlength', $('#first-name').attr("maxlength"));
or you can take a generic approach like this:
$(function(){
$("input[class*='easyui-textbox'][maxlength][id]").each(function (i, elt) { // iterate all jeasyui textboxes having maxlength attribute and id attribute
// alert("found : " + elt.id );
$('#' + elt.id).textbox();
$('#' + elt.id).textbox('textbox').attr('maxlength', $('#' + elt.id).attr("maxlength"));
});
});