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<!DOCTYPE html> <html> <head> <script src="/lib/jquery-1.12.2.min.js"></script> <script> $(document).ready(function(){ $("button").click(function(){ $("div").width(function(n, c){ return c - 200; }); }); }); </script> </head> <body> <button>Decrease width of div with 200 px.</button><br><br> <div style="height:100px;border:4px solid;"></div> </body> </html>