[JS ] Binary Search Tree iterator to find the next smallest number

BSTSmallestGenerator.js

class BSTIterator {
  constructor(root) {
    this.nextValue = null; 
    this.sortedValues = getInOrderValues(root);
  }
  
  hasNext() {
    if(!this.nextValue) {      
      const next = this.sortedValues.next();
      this.nextValue = next.done ? null : next.value;
    }
    return this.nextValue !== null;
  }
  
  next() {
    if(this.hasNext()) {
      const aux = this.nextValue;
      this.nextValue = null;
      return aux;
    }
    return  null;
  }
}


function* getInOrderValues(root) {
  if(root) {    
    if(root.left) {
      yield * getInOrderValues(root.left);
    }
    yield root.data;
    if(root.right) {
      yield * getInOrderValues(root.right);
    }  
  }
}


// ---------------------------------- Test ---------------------------------//
class Node {
  constructor(data) {
    this.data = data; 
    this.left = null;
    this.right = null;
  }
}
const root = new Node(7);
const node5 = new Node(5);
const node20 = new Node(20);
const node18 = new Node(18);
const node25 = new Node(25);
root.left = node5;
root.right = node20;
node20.left = node18;
node20.right = node25;
  //   7
  //  / \
  // 5  20
  //   /  \
  //  18   25

const iterator = new BSTIterator(root);
console.log(iterator.next());    //  5
console.log(iterator.next());    //  7
console.log(iterator.hasNext()); //  true
console.log(iterator.next());    //  18
console.log(iterator.hasNext()); //  true
console.log(iterator.next());    //  20
console.log(iterator.hasNext()); //  true
console.log(iterator.next());    //  25
console.log(iterator.hasNext()); //  false