linked-list.js

const Node = function(value, next) {
  this.value = value;
  this.next = next;
};

const List = function() {
  this.length = 0;
  this.head = null;
};

List.prototype.add = function(value) {
  if (!this.head) {
    this.head = new Node(value);
  } else {
    let curr = this.head;
    while (curr.next) {
      curr = curr.next;
    }
    curr.next = new Node(value);
  }
  this.length++;
};

List.prototype.remove = function(value) {
  let current = this.head;
  let previous;
  if (current.value === value){
    this.head = current.next;
  } else {
    while (current.value !== value) {
      previous = current;
      current = current.next;
    }
    previous.next = current.next;
  }
  this.length--;
};

List.prototype.getAt = function(i) {
  let current = this.head;
  for (let c = 0; c < i; c++) {
    current = current.next;
  }
  return current.value;
};

List.prototype.removeAt = function(i) {
  let current = this.head;
  let previous;
  for (let c = 0; c < i; c++) {
    previous = current;
    current = current.next;
  }
  previous.next = current.next;
  this.length--;
};

List.prototype[Symbol.iterator] = function* () {
  let current = this.head;
  while (current) {
    yield current.value;
    current = current.next;
  }
};

const list = new List;

list.add(55);
list.add(20);
list.add(11);
list.add(22);

console.log('iterator:');

for (let el of list) {
  console.log(el);
}

console.log('getAt():');

console.log(0, list.getAt(0));
console.log(1, list.getAt(1));
console.log(3, list.getAt(3));

list.removeAt(1);

console.log('removing index 1');

for (let el of list) {
  console.log(el);
}

console.log('removing value 55');

list.remove(55);
for (let el of list) {
  console.log(el);
}