jquery variable in css (left: - "DivWidth")

jquery variable in css (left: - "DivWidth")

Hi, im in the process of coding up a sliding out menu. at the moment i am getting the div width in jquery like this 

  1. var Menuwidth = $('.SidebarWrapper').width();
The width is 280px, but when developing new sites it could be different. this is obviously adjusted in the CSS file. How do i add the variable into CSS with a negative value equal to "Menuwidth"

  1. $(window).resize(function (){
  2.     $(Sidebarwrapper).css({
  3.         'transition' : 'all 0.4s ease 0s',
  4.         'left' : '- + Menuwidth +' /*This needs to be -280px*/
  5.     });
  6. });
Any help would be greatly appreciated.