tdubs42/doubly-linked-list-class.js

## doubly-linked-list-class.js
const Node = require('./Node');

class DoublyLinkedList {
  constructor() {
    this.head = null;
    this.tail = null;
  }

  addToHead(data) {
    const newHead = new Node(data);
    const currentHead = this.head;
    if (currentHead) {
      currentHead.setPreviousNode(newHead);
      newHead.setNextNode(currentHead);
    }
    this.head = newHead;
    if (!this.tail) {
      this.tail = newHead;
    }
  }

  addToTail(data) {
    const newTail = new Node(data);
    const currentTail = this.tail;
    if (currentTail) {
      currentTail.setNextNode(newTail);
      newTail.setPreviousNode(currentTail);
    }
    this.tail = newTail;
    if (!this.head) {
      this.head = newTail;
    }
  }

  removeHead() {
    const removedHead = this.head;
    if (!removedHead) {
      return;
    }
    this.head = removedHead.getNextNode();
    if (this.head) {
      this.head.setPreviousNode(null);
    }
    if (removedHead === this.tail) {
      this.removeTail();
    }
    return removedHead.data;
  }

  removeTail() {
    const removedTail = this.tail;
    if (!removedTail) {
      return;
    }
    this.tail = removedTail.getPreviousNode();
    if (this.tail) {
      this.tail.setNextNode(null);
    }
    if (removedTail === this.head) {
      this.removeHead();
    }
    return removedTail.data;
  }

  removeByData(data) {
    let nodeToRemove;
    let currentNode = this.head;
    while (currentNode !== null) {
      if (currentNode.data === data) {
        nodeToRemove = currentNode;
        break;
      }
      currentNode = currentNode.getNextNode();
    }
    if (!nodeToRemove) {
      return null;
    }
    if (nodeToRemove === this.head) {
      this.removeHead();
    } else if (nodeToRemove === this.tail) {
      this.removeTail();
    } else {
      const nextNode = nodeToRemove.getNextNode();
      const previousNode = nodeToRemove.getPreviousNode();
      nextNode.setPreviousNode(previousNode);
      previousNode.setNextNode(nextNode);
    }
    return nodeToRemove;
  }

  printList() {
    let currentNode = this.head;
    let output = '<head> ';
    while (currentNode !== null) {
      output += currentNode.data + ' ';
      currentNode = currentNode.getNextNode();
    }
    output += '<tail>';
    console.log(output);
  }
}
const subway = new DoublyLinkedList()


module.exports = DoublyLinkedList;
	const Node = require('./Node');

	class DoublyLinkedList {
	constructor() {
	this.head = null;
	this.tail = null;
	}

	addToHead(data) {
	const newHead = new Node(data);
	const currentHead = this.head;
	if (currentHead) {
	currentHead.setPreviousNode(newHead);
	newHead.setNextNode(currentHead);
	}
	this.head = newHead;
	if (!this.tail) {
	this.tail = newHead;
	}
	}

	addToTail(data) {
	const newTail = new Node(data);
	const currentTail = this.tail;
	if (currentTail) {
	currentTail.setNextNode(newTail);
	newTail.setPreviousNode(currentTail);
	}
	this.tail = newTail;
	if (!this.head) {
	this.head = newTail;
	}
	}

	removeHead() {
	const removedHead = this.head;
	if (!removedHead) {
	return;
	}
	this.head = removedHead.getNextNode();
	if (this.head) {
	this.head.setPreviousNode(null);
	}
	if (removedHead === this.tail) {
	this.removeTail();
	}
	return removedHead.data;
	}

	removeTail() {
	const removedTail = this.tail;
	if (!removedTail) {
	return;
	}
	this.tail = removedTail.getPreviousNode();
	if (this.tail) {
	this.tail.setNextNode(null);
	}
	if (removedTail === this.head) {
	this.removeHead();
	}
	return removedTail.data;
	}

	removeByData(data) {
	let nodeToRemove;
	let currentNode = this.head;
	while (currentNode !== null) {
	if (currentNode.data === data) {
	nodeToRemove = currentNode;
	break;
	}
	currentNode = currentNode.getNextNode();
	}
	if (!nodeToRemove) {
	return null;
	}
	if (nodeToRemove === this.head) {
	this.removeHead();
	} else if (nodeToRemove === this.tail) {
	this.removeTail();
	} else {
	const nextNode = nodeToRemove.getNextNode();
	const previousNode = nodeToRemove.getPreviousNode();
	nextNode.setPreviousNode(previousNode);
	previousNode.setNextNode(nextNode);
	}
	return nodeToRemove;
	}

	printList() {
	let currentNode = this.head;
	let output = '<head> ';
	while (currentNode !== null) {
	output += currentNode.data + ' ';
	currentNode = currentNode.getNextNode();
	}
	output += '<tail>';
	console.log(output);
	}
	}
	const subway = new DoublyLinkedList()


	module.exports = DoublyLinkedList;