if(localStorage.getItem("counter")){
  if((localStorage.getItem("counter") >= 300) || (localStorage.getItem("counter") <= 0)){
    var value = 300;
  }else{
    var value = localStorage.getItem("counter");
  }
}else{
  var value = 300;
}
document.getElementById('divCounter').innerHTML = value;

var counter = function (){
  if(value <= 0){
    localStorage.setItem("counter", 0);
    value = 0;
    $( ".exit" ).trigger( "click" );
  }else{
    value = parseInt(value)-1;
    localStorage.setItem("counter", value);
  }
  document.getElementById('divCounter').innerHTML = value;
};

var interval = setInterval(function (){counter();}, 1000);