Know word at text insertion pointer on a webpage?

I would like to know the word at the position of the text insertion pointer in a form on a webpa开发者_Python百科ge. My problem is that I don't really know what language to use to do this, and I have no idea how to do it in Javascript.

Any ideas?

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get caret position javascript IE firefox

http://blog.vishalon.net/index.php/javascript-getting-and-setting-caret-position-in-textarea/

Here is how to find moused over word on page

How to get a word under cursor using JavaScript?