Jquery Cookies

Im creating a mobile apps using Icenium(html,css,jquery mobile,java script). One of the features of my apps is to have a save username and password of persons who log-in. and many said it will work using plugin. But i tried many plugin but it didnt work. Is there anything you can help about my problem?a example of simple code when use cookies taht will work in my apps. Hope you can help me. Thanks