
((window.gitter = {}).chat = {}).options = {
  room: 'thepracticaldev/1pr',
  useStyles: false
};


function toggleSidebar(){

  sidebar     = document.getElementById("sidebar"),
  mainContent = document.getElementById("main-content");

	if( window.width < 768 ){
		if (sidebar.style.display == 'none') {
			sidebar.style.display = 'block';
			mainContent.style.marginLeft = "200px";
		} else {
			sidebar.style.display = 'none';
			mainContent.style.marginLeft = "0px";
		}
	}
}


((window.gitter = {}).chat = {}).options = {
  room: 'thepracticaldev/1pr',
  useStyles: false
};


function toggleSidebar(){

	sidebar     = document.getElementById("sidebar"),
	mainContent = document.getElementById("main-content");

	if( window.width < 768 ){
		if (sidebar.style.display == 'none') {
			sidebar.style.display = 'block';
		} else {
			sidebar.style.display = 'none';
		}
	}
}

Update main.js