Doesn't delete item when manually added

//Problem: User interaction doesn't provide desired results
//Solution: Add the interactivity so the user can solve daily tasks

var taskInput = document.getElementById("new-task"); //new-task
var addButton = document.getElementsByTagName("button")[0]; //First button
var incompleteTaskHolder = document.getElementById("incomplete-tasks"); //incomplete-tasks
var completedTaskHolder = document.getElementById("completed-tasks"); //completed-tasks

//New Task List Item
var createNewTaskElement = function(taskString) {
    //Create List Item
    var listItem = document.createElement("li");

    //input (checkbox)
    var checkBox = document.createElement("input"); //Checkbox
    //label
    var label = document.createElement("label");
    //input text
    var editInput = document.createElement("input"); //text
    //button.edit
    var editButton = document.createElement("button");
    //button.delete
    var deleteButton = document.createElement("button");

    //Each element needs modifying
    checkBox.type = "checkBox";
    editInput.type = "text";

    editButton.innerText = "Edit";
    editButton.className = "Edit";
    deleteButton.innerText = "Delete";
    deleteButton.className = "Delete";

    label.textContent = taskString;

    //Each element needs appending
    listItem.appendChild(checkBox);
    listItem.appendChild(label);
    listItem.appendChild(editInput);
    listItem.appendChild(editButton);
    listItem.appendChild(deleteButton);

    return listItem;
};

//Add a new task
var addTask = function() {
  //When the button is pressed

  //Create a new list item with the text from #new-task:
  var listItem = createNewTaskElement(taskInput.value);

  //Append listItem to incompleteTaskHolder
  incompleteTaskHolder.appendChild(listItem);
};

//Edit an existing task
var editTask = function() {
  //When the edit button is pressed
    //if the class of the parent is .editMode
      //Switch from .editMode
      //Label text become the input's value
    //else
      //Switch to .editMode
      //Input value becomes the label's text

    //Toglle .editMode on the parent
};

//Delete an exisitng task
var deleteTask = function() {
  var listItem = this.parentNode;
  var ul = listItem.parentNode;

  //Remove the parent list item from the ul
  ul.removeChild(listItem);
};

//Mark a task as complete
var taskCompleted = function() {
  //Append the task list item to the #completed-task
  var listItem = this.parentNode;
  completedTaskHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskIncomplete);
};

//Mark a tast as incomplete
var taskIncomplete = function() {
  //Append the task list item to the #incomplete-task
  var listItem = this.parentNode;
  incompleteTaskHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskCompleted);
};

var bindTaskEvents = function(taskListItem, checkBoxEventHandler){
//select taskListItem's children
var checkBox = taskListItem.querySelector("input[type=checkbox]");
var editButton = taskListItem.querySelector("button.edit");
var deleteButton = taskListItem.querySelector("button.delete");
  //bind editTask to edit button
  editButton.onclick = editTask;

  //bind deleteTask to dellete button
  deleteButton.onclick = deleteTask;

  //bind checkBoxEventHandler to checkbox
  checkBox.onchange = checkBoxEventHandler;
}; 

//Set the click handler to the addTask function
addButton.onclick = addTask;

//Cycle over incompleteTaskHolder ul list items
for (var i = 0; i < incompleteTaskHolder.children.length; i++){
  //bind events to list item's children (taskCompleted) 
  bindTaskEvents(incompleteTaskHolder.children[i], taskCompleted);
};

//Cycle over completedTaskHolder ul list items
for (var i = 0; i < completedTaskHolder.children.length; i++){
  //bind events to list item's children (taskIncomplete) 
  bindTaskEvents(completedTaskHolder.children[i], taskIncomplete);
}