Implement Stack interface using linked list

linked-list-as-stack.js

// linked-list-as-stack

function stack() {
  this.head = null;
}

stack.prototype.print = function() {
  let curr = this.head
  while(curr) {
    console.log(curr.val)
    curr = curr.next
  }
}

stack.prototype.push = function(val) {
  if (!this.head) {
    this.head = {
      val: val,
      next: null
    }
  } else {
    let pushed = {
      val: val,
      next: this.head
    }
    this.head = pushed;
  }
}

stack.prototype.pull = function() {
  let pulled;
  if (!this.head) {
    pulled = null;
  } else {
    pulled = this.head;
    this.head = this.head.next;
  }
  return pulled;
}


let st = new stack();
st.push(5);
st.push(4);
st.push(3);
st.push(2);
st.push(1);

st.print();

st.pull();
st.print();