JQUery validation plugin for checking data availability

I am learning how to use JQuery validation plugin, I got a simple input text field like this:

<input type="text" name="username">

But I don't know how to use this plugin to do some data开发者_JAVA百科 availability tasks.

Could you help me please?

The remote methods looks like the tool for the job. It makes requests to a URL you specify to implement server-side validation.