-  + 

(function(){
   var subBtn=document.getElementById('sub'); var span=document.getElementById('num'); var addBtn=document.getElementById('add'); if(localStorage.num===undefined){ localStorage.num=0; } span.innerHTML=localStorage.num; subBtn.addEventListener('click',function(){ localStorage.num--; span.innerHTML=localStorage.num; },false); addBtn.addEventListener('click',function(){ localStorage.num++; span.innerHTML=localStorage.num; },false); })();