linkedList.js

<script type="text/javascript">
  function Item(value){
    this.value = value;
    this.next = null;
  }

  function List(value) {
    this.head = new Item(value);
    this.tail = null;
    this.length = 1;

    this.add=function(value){
      var item = new Item(value);
      if (this.tail == null){
        this.head.next = item;
      }
      else{
        this.tail.next = item;
      }
      this.tail = item;
      this.length += 1;
    }

    this.itemAt=function(index){
      if (index >= this.length){
        return "no item in position " + index;
      }
      var curr = 0;
      var item = this.head;
      while (curr != index)
      {
        item = item.next;
        curr += 1;
      }
      return "item at position " + index + " equals " + item.value;
    }

    this.iterate = function(action){
      var item = this.head;
      action(item.value);
      
      while(item.next){
        item=item.next;
        action(item.value);
      }
    }

    this.print = function(){
      var began = false;
      this.iterate(function(item){ 
          if (began) document.write(" => ");
          document.write(item);
          began = true;
      });
    }

    this.printReverse=function(){
      var itens = [];
      this.iterate(function(item){
          itens.push(item);
      });
      itens.reverse();
      for (var i=0;i<itens.length;i++){
        document.write(itens[i]);
        
        if (i != itens.length-1)
          document.write(" => ");
      }

    }
  }

  var list = new List(1);
  list.add(22);
  list.add(333);
  list.add(4444);
  list.add(55555);

  list.print();
  
  document.write("<br>");
  
  list.printReverse();
  
  document.write("<br> we have " + list.length + " itens");
  
  document.write("<br> " + list.itemAt(10));
  document.write("<br> " + list.itemAt(0));
  document.write("<br> " + list.itemAt(1));
  document.write("<br> " + list.itemAt(3));
  document.write("<br> " + list.itemAt(list.length));
</script>