如何在文本域Appcelerator中输入文本后验证电子邮件

I am new in appcelerator. I have a doubt. Does anybody have any idea about how to check email validation after we entered text in text field. I can able to do by a button click. But what i want is that, need to check in text field itself after text is entered. Any help will be deeply appreciated.I am new in appcelerator. I have a doubt. Does