class Node {
	constructor(data) {
		this.data = data;
		this.left = null;
		this.right = null;
		this.parent = null;
	}
}

class BST {
	constructor(data) {
		this._root = new Node(data);
	}

recurseAdd(data, currNode=this._root) {
	let newNode = new Node(data);

	if (data <= currNode.data) {
		// leftNode - empty
		if(!currNode.left) {
			currNode.left = newNode;
			newNode.parent = currNode;
			// leftNode - exists
		} else {
			currNode = currNode.left;
			this.recurseAdd(data, currNode);
		}
	} else {
		// leftNode - empty
		if(!currNode.right) {
			newNode.parent = currNode;
			currNode.right = newNode;
			// leftNode - exists
		} else {
			currNode = currNode.right;
			this.recurseAdd(data, currNode);
		}
	}
}

add(data, currNode=this._root) {
	let newNode = new Node(data);

	while(currNode) {
		if (data <=currNode.data) {
		// leftNode - empty
		if (!currNode.left) {
			newNode.parent = currNode;
			currNode.left = newNode;
			break;
			// leftNode - exists
		} else {
			currNode = currNode.left;
		}
	} else {
		// leftNode - empty
		if (!currNode.right) {
		  newNode.parent = currNode;
			currNode.right = newNode;
			break;
			// leftNode - exists
		} else {
			currNode = currNode.right;
		}
	}	// end of outer-most else
	} // end of while

}	// end of iterative ADD

/* PRINT OUT VALUES - BFS Traversal */
BFS(currNode=this._root, queue=[], results=[]) {
	if (currNode === null) {return;}

	// push rootNode to stack
	queue.push(currNode);
	let len = queue.length;

	while (queue.length !== 0) {
		// check if left child exists
		if (currNode.left) {
			queue.push(currNode.left);
		}
		// check if right child exists
		if (currNode.right) {
			queue.push(currNode.right);
		}

	// remove 'first element' in [queue]
	let node = queue.shift();
	let nodeVal = node.data;
	//console.log(`nodeVal: ${nodeVal}`);
		results.push(nodeVal);
		currNode = queue[0];
	} // end of while-loop

	return results;
} // end of BFS
}

let hi = new BST('f');
hi.add('d');
hi.add('k');

hi.add('b');
hi.add('e');
hi.add('g');
hi.add('l');

hi.add('a');
hi.add('c');
hi.add('h');

hi.add('j');
/* console.log(hi._root); */

// BFS
let result = hi.BFS();
console.log(`Printed Values in BFS: [${result}]`);