"this" refrencing click event inside class method

Question

I refactored the code to be able to create multiple instances of a To Do List by encapusalting the logic in a class. The concept of the To Do List is that you can drag a To Do Item from one column to another and it will change color and place, depending on which column it is dragged to.

Each list has a instance of the TaskManager class to handle the individual eventListeners and querySelectors.

The problem is that now when i use "this" keyword in deleteButtonClick or taskClick method i get "this.getAttribute is not a function" And when i drag the To Do Item it changes color but not place.

Before "this" was references the item clicked, but now i am not sure what it is refrencing.

"use strict";

class TaskManager {
  constructor(identifier) {
    this.identifier = identifier;
    this.addTaskText = "Add";
    this.updateTaskText = "Update";
    this.TodoContent = document.querySelector(`.${this.identifier}`);
    this.toDoList = this.TodoContent.querySelector(".toDoList");
    this.draggedTask = {};
    this.toDoListHeight = this.toDoList.offsetHeight;
    this.ongoingListHeight = 0;
    this.doneListHeight = 0;

    document.addEventListener("DOMContentLoaded", () => {
      const currentTask = this.TodoContent.querySelector(".currentTask");
      currentTask.setAttribute("currentid", "");
      currentTask.setAttribute("lastid", "0");
    });

    this.TodoContent.querySelector(".addTask").addEventListener("click", () => this.addTask());

    this.TodoContent.querySelector(".btnOk").addEventListener("click", () => this.handleTaskButton());

    this.TodoContent.querySelector(".btnCancel").addEventListener("click", () => this.cancelTaskEdition());
    this.TodoContent.querySelector(".txtTask").addEventListener("keyup", (e) =>
      e.code === "Escape" ? this.cancelTaskEdition() : true
    );

    this.TodoContent.querySelector(".showHelp").addEventListener("click", () => this.showHelp());

    const btnClose = this.TodoContent.querySelector(".btnClose");
    btnClose.addEventListener("click", () => this.hideHelp());
    btnClose.addEventListener("keyup", (e) => (e.code === "Escape" ? this.hideHelp() : true));

    this.TodoContent.querySelectorAll(".listColumn").forEach((list) => {
      list.addEventListener("dragover", (e) => e.preventDefault());
    });

    this.TodoContent.querySelector(".toDoList").addEventListener("drop", () => this.dropTask("toDo"));
    this.TodoContent.querySelector(".ongoingList").addEventListener("drop", () => this.dropTask("ongoing"));
    this.TodoContent.querySelector(".doneList").addEventListener("drop", () => this.dropTask("done"));
  }

  addTask() {
    const currentTask = this.TodoContent.querySelector(".currentTask");
    const txtTask = this.TodoContent.querySelector(".txtTask");
    const newID = parseInt(currentTask.getAttribute("lastid")) + 1;

    txtTask.value = "";
    this.TodoContent.querySelector(".btnOk").value = this.addTaskText;
    currentTask.setAttribute("currentid", newID);
    currentTask.style.display = "block";
    txtTask.focus();
  }

  taskClick() {
    const currentTask = this.TodoContent.querySelector(".currentTask");
    const txtTask = this.TodoContent.querySelector(".txtTask");
    const ID = parseInt(this.getAttribute("taskId"));

    this.TodoContent.querySelector(".btnOk").value = this.updateTaskText;
    txtTask.value = this.innerText;
    currentTask.setAttribute("currentid", ID);
    currentTask.style.display = "block";
    txtTask.focus();
  }

  deleteButtonClick(e) {
    e.stopPropagation();
    const taskHeight = this.parentElement.offsetHeight + 10;
    const currentListName = this.parentElement.parentElement.id;

    this.parentElement.remove();

    switch (currentListName) {
      case "toDoList":
        this.toDoListHeight -= taskHeight;
        break;
      case "ongoingList":
        this.ongoingListHeight -= taskHeight;
        break;
      case "doneList":
        this.doneListHeight -= taskHeight;
        break;
    }
    this.resizeLists();
  }

  handleTaskButton() {
    const taskText = this.TodoContent.querySelector(".txtTask");
    const currentTask = this.TodoContent.querySelector(".currentTask");

    if (taskText.value.trim() === "") {
      taskText.focus();
      return false;
    }

    if (this.TodoContent.querySelector(".btnOk").value === this.addTaskText) {
      this.addTaskToList();
    } else {
      this.updateTask();
    }

    taskText.value = "";
    currentTask.style.display = "none";
  }

  addTaskToList() {
    const task = document.createElement("div");
    const taskText = this.TodoContent.querySelector(".txtTask");
    const currentTask = this.TodoContent.querySelector(".currentTask");
    const newID = parseInt(currentTask.getAttribute("currentid")) + 1;

    task.classList.add("task");
    task.classList.add("toDo");
    task.innerText = taskText.value;
    task.setAttribute("taskId", currentTask.getAttribute("currentid"));
    currentTask.setAttribute("lastid", newID);
    task.addEventListener("click", () => this.taskClick());
    task.setAttribute("draggable", "true");
    task.addEventListener("dragstart", (e) => this.dragStart(e));
    task.prepend(this.deleteButton());

    this.toDoList.prepend(task);
    this.toDoListHeight += task.offsetHeight + 10;
    this.resizeLists();
  }

  updateTask() {
    const taskText = this.TodoContent.querySelector(".txtTask");
    const currentTask = this.TodoContent.querySelector(".currentTask");
    const task = this.TodoContent.querySelector('div.task[taskid="' + currentTask.getAttribute("currentid") + '"]');
    const previousHeight = task.offsetHeight;
    const currentListName = task.parentNode.id;

    task.innerText = taskText.value;
    task.prepend(this.deleteButton());

    switch (currentListName) {
      case "toDoList":
        this.toDoListHeight = this.toDoListHeight - previousHeight + task.offsetHeight;
        break;
      case "ongoingList":
        this.ongoingListHeight = this.ongoingListHeight - previousHeight + task.offsetHeight;
        break;
      case "doneList":
        this.doneListHeight = this.doneListHeight - previousHeight + task.offsetHeight;
    }

    this.resizeLists();
  }

  cancelTaskEdition() {
    const currentTask = this.TodoContent.querySelector(".currentTask");
    currentTask.setAttribute("currentid", "0");
    currentTask.style.display = "none";
  }

  showHelp() {
    this.TodoContent.querySelector(".help").style.display = "block";
    this.TodoContent.querySelector(".btnClose").focus();
  }

  hideHelp() {
    this.TodoContent.querySelector(".help").style.display = "none";
  }

  dragStart(e) {
    e.dataTransfer.setData("text/plain", null);
    this.draggedTask = e.target;
  }

  dropTask(listName) {
    const taskList = this.draggedTask.parentNode.id;

    if (taskList !== listName + "List") {
      const taskHeight = this.draggedTask.offsetHeight + 10;

      this.draggedTask.parentNode.removeChild(this.draggedTask);

      switch (taskList) {
        case "toDoList":
          this.toDoListHeight -= taskHeight;
          break;
        case "ongoingList":
          this.ongoingListHeight -= taskHeight;
          break;
        case "doneList":
          this.doneListHeight -= taskHeight;
          break;
      }

      this.draggedTask.classList.remove("toDo", "ongoing", "done");
      this.draggedTask.classList.add(listName);
      this.toDoList.appendChild(this.draggedTask);

      switch (listName) {
        case "toDo":
          this.toDoListHeight += taskHeight;
          break;
        case "ongoing":
          this.ongoingListHeight += taskHeight;
          break;
        case "done":
          this.doneListHeight += taskHeight;
          break;
      }

      this.resizeLists();
    }
  }

  deleteButton() {
    const deleteButton = document.createElement("a");

    deleteButton.classList.add("deleteButton");
    deleteButton.addEventListener("click", (e) => this.deleteButtonClick(e));

    return deleteButton;
  }

  resizeLists() {
    const higherListHeight = Math.max(this.toDoListHeight, this.ongoingListHeight, this.doneListHeight);

    this.TodoContent.querySelectorAll(".listColumn").forEach((list) => {
      list.style.height = higherListHeight + "px";
    });

    this.TodoContent.querySelector(".listContent").style.height = higherListHeight + 20 + "px";
  }
}

class TaskManagerManager {
  constructor() {
    this.taskManagers = [];
    //ensure incrementing id
    this.countArray = [];
  }
  count() {
    return this.countArray.length;
  }

  createTaskManager(identifier) {
    this.identifier = identifier;
    console.log(this.identifier);
    const taskManager = new TaskManager(this.identifier);
    this.taskManagers.push(taskManager);
    this.countArray.push(0);
    return taskManager;
  }
}

const taskManagerManager = new TaskManagerManager();
const taskManager1 = taskManagerManager.createTaskManager("contentWrapper");

document.querySelector("#new_todo").addEventListener("click", createList);
async function createList() {
  const newId = await newList();
  console.log(newId);
  const taskManager = taskManagerManager.createTaskManager(newId);
  async function newList() {
    const cloneContainer = document.querySelector(".clone");
    const clone = cloneContainer.cloneNode(true);

    const elementsToRemove = clone.querySelectorAll(`[taskid]`);
    elementsToRemove.forEach((element) => {
      element.parentNode.removeChild(element);
    });

    const todoContent = clone.querySelector(".contentWrapper");
    const newId = "todoContent" + (taskManagerManager.count() + 1);
    todoContent.classList.add(newId);
    console.log(newId);

    // Create TaskManager after updating the id
    cloneContainer.parentNode.appendChild(clone);
    return newId;
  }
}

@import url("https://fonts.googleapis.com/css2?family=Raleway:wght@400&display=swap");

:root {
  --colorTextSecondary: floralwhite;

  --colorPrimary: blue;
  --colorSecondary: white;
  --colorTertiary: yellow;

  --colorToDo: lightsalmon;
  --colorOngoing: palegoldenrod;
  --colorDone: lightgreen;

  --imgDelete: url(../img/trash.png);
}

* {
  margin: 0;
  box-sizing: border-box;
}

body {
  font-family: "Raleway", Arial, Helvetica, sans-serif;
}

header {
  padding: 0.5rem 0 0.5rem 0.5rem;
  color: var(--colorTextSecondary);
  background-color: var(--colorPrimary);
}
header > h1 {
  text-indent: 2rem;
}

main {
  padding: 0.5rem;
  line-height: 1.4rem;
}

footer {
  position: fixed;
  bottom: 0;
  width: 100%;
  padding: 0.25rem 0 0.25rem 0;
  color: var(--colorTextSecondary);
  background-color: var(--colorPrimary);
  text-align: center;
}

header.listHeaders {
  border-radius: 0.5rem 0.5rem 0 0;
  color: var(--colorPrimary);
  background-color: var(--colorTertiary);
  font-weight: bold;
}
div.toDoHeader {
  float: left;
  width: 33%;
}
div.ongoingHeader {
  float: left;
  width: 33%;
}
div.toDoList {
  float: left;
  width: 33%;
}
div.ongoingList {
  float: left;
  width: 33%;
}
div.doneList {
  float: left;
  width: 33%;
}

main.listContent {
  min-height: 40px;
  padding-right: 0;
  overflow: auto;
}

.clone {
  border-radius: 0.5rem 0.5rem 0.5rem 0.5rem;
  background-color: var(--colorSecondary);
}

a {
  color: var(--colorPrimary);
  background-color: var(--colorTextSecondary);
  text-align: center;
  border-radius: 0.25rem;
}
a:hover {
  cursor: pointer;
  background-color: var(--colorTertiary);
}

.buttons {
  display: flex;
  padding: 10px;
  justify-content: space-between;
}
.buttons a {
  margin-right: 10px;
}
#new_todo {
  display: inline-block;
  width: 25%;
  border-radius: 0.25rem;

  line-height: 2rem;
}
a.addTask {
  display: inline-block;
  width: 25%;
  border-radius: 0.25rem;
  font-size: 3rem;
  line-height: 2rem;
}
a.save {
  display: inline-block;
  width: 25%;
  border-radius: 0.25rem;
  font-size: 1rem;
  line-height: 2rem;
  font-weight: 600;
  color: rgb(171, 21, 21);
}

a.showHelp {
  display: block;
  float: right;
  margin-right: 1rem;
  padding: 0.5rem;
  font-size: 1.2rem;
}
a.deleteButton {
  display: block;
  float: right;
  width: 1.5rem;
  height: 1.5rem;
  margin-left: 0.25rem;
  background-image: var(--imgDelete);
}

div.modal {
  display: none;
  position: fixed;
  z-index: 1;
  top: 3.5rem;
  border: solid thick var(--colorPrimary);
  border-radius: 0.5rem;
  padding: 0.25rem;
  width: 80%;
  height: 80%;
  left: 10%;
  background-color: var(--colorTextSecondary);
}
@media (min-width: 768px) {
  div.task {
    width: 60%;
    left: 20%;
  }
}
@media (max-height: 480px) {
  div.task {
    height: 60%;
  }
}
div.help {
  left: 20%;
  width: 60%;
  height: auto;
}
p.helpText {
  margin-bottom: 0.5rem;
}

textarea.txtTask {
  width: 99%;
  height: 92%;
  resize: none;
  overflow: auto;
  border-color: var(--colorSecondary);
}

input[type="button"] {
  padding: 0.25rem 1rem;
  font-size: 1rem;
  font-weight: bold;
  border: none;
  border-radius: 0.25rem;
  cursor: pointer;
}
div.buttons {
  padding-right: 2rem;
  text-align: right;
}

div.task {
  border: thin solid var(--colorPrimary);
  border-radius: 0.25rem;
  margin-bottom: 0.5rem;
  padding: 0.25rem;
  width: 95%;
  max-height: 10rem;
  overflow: auto;
  word-wrap: break-word;
  cursor: pointer;
}
div.toDo {
  background-color: var(--colorToDo);
}
div.ongoing {
  background-color: var(--colorOngoing);
}
div.done {
  background-color: var(--colorDone);
}

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>To Do List</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <meta name="author" content="Arturo Mora-Rioja" />
    <meta name="description" content="A simple to do list with three possible states: to do, ongoing, done" />
    <link rel="stylesheet" href="css/styles.css" />
    <script src="js/script.js" defer></script>
  </head>
  <body>
    <header>
      <h1>To Do List</h1>
          <a id="new_todo">New list</a>
    </header>
    <div class="clone">
      <div class="contentWrapper">


      <a class="showHelp">Help</a>
      <div>
        <header class="listHeaders">
          <div class="toDoHeader listHeader">To do</div>
          <div class="ongoingHeader listHeader">Ongoing</div>
          <div class="doneHeader listHeader">Done</div>
        </header>
        <main class="listContent">
          <div class="toDoList listColumn"></div>
          <div class="ongoingList listColumn"></div>
          <div class="doneList listColumn"></div>
        </main>
        <div class="currentTask modal">
          <textarea class="txtTask"></textarea><br />
          <div class="buttons">
            <input type="button" class="btnOk" value="Add" />
            <input type="button" class="btnCancel" value="Cancel" />
          </div>
        </div>
        <div class="buttons"><a class="addTask">+</a>
      </div>

      <div class="help modal">
        <p class="helpText">
          Add a new "to do" task by pressing the plus ("+") button.<br />
          Move a task from one area to another ("to do", "ongoing", "done") by dragging and dropping it.
        </p>
        <div class="buttons">
          <input type="button" class="btnClose" value="Close" />
        </div>
      </div>
    </div>
    </main>

    <footer>footer</footer>
  </body>
</html>