One way to use RWD in JS.

myScriptyStuff.js

jQuery(function ($) {
  
  var width = window.innerWidth ? window.innerWidth : $(window).width(),
      height = window.innerHeight ? window.innerHeight : $(window).height(),
      touch = Modernizr.touch;
  
  var breakpoint = function() {
    if (width < 768) {
      return 'small';
    } else if (width < 992 ) {
      return 'medium';
    } else if (width < 1200 ) {
      return 'large';
    } else if (width < 1600 ) {
      return 'x-large';
    } else if (width >= 1600) {
      return 'xx-large';
    }

  }

  // Paul Irish Smart Resize plug in http://paulirish.com/2009/throttled-smartresize-jquery-event-handler/
  $(window).smartresize(function(){
    width = window.innerWidth ? window.innerWidth : $(window).width();
    height = window.innerHeight ? window.innerHeight : $(window).height();
    
    breakpoint();
  });
  
  if (!touch && ( breakpoint() != 'small' )) {
    //I'm not a small display and I probably use a mouse
  }
});