Scale image as background based upon user's machine screensize

I have a image (uploaded by user, cant say about the size of that). It will be used as background image for his page. I just want to scale it to the full size of the screen. Some think like. On load find the screensize using Jquery/javascript and add that style to the background ima开发者_StackOverflow中文版ge.

PS:- There is no Y scroll on the page. And I am not concerned about the quality of the image on scaling if image size of too small.

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Check out this jQuery plugin https://github.com/iamjpg/jQuery-Ez-Background-Resize