$(document).ready(function(){
    $(".sidenav a").click(handleClick);      
    hideAll();
    $($(".section")[0]).show();
    $("#"+$(".section")[0].id.split("_")[0]).addClass("currentSelection");
});
function hideAll(){
  $(".section").each(function(i){
   $(this).hide();
  });
}
function handleClick(){
  if($('#'+this.id).attr('class')=="currentSelection")
    return;
  hideAll();
  $(".sidenav a").removeClass();
  $('#'+this.id+"_content").slideDown(500);
  $('#'+this.id).addClass("currentSelection");
}