Marking items as complete works but not the other way around

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

var taskInput = document.getElementById("new-task"); //new-task
var addButton = document.getElementsByTagName("button")[0]; //first button
var incompleteTasksHolder = document.getElementById("incomplete-tasks"); //incomplete-tasks
var completedTasksHolder = 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");
  // button.edit
  var editButton = document.createElement("button");
  // button.delete
  var deleteButton = document.createElement("button");

  // Each elements needs modifing

  // 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() {
  console.log("add task...");
  // Create a new list item with the text from #new-task:
  var listItem = createNewTaskElement("Some new task");

  // Append list item to incompleteTaskHolder
  incompleteTasksHolder.appendChild(listItem)
  bindTaskEvents(listItem, taskCompleted);
}

// Edit an existing task
var editTask = function() {
  console.log("edit task...");
  // When the edit Button is pressed
    // if the class of the parent is .editMode
      // Switch from .editMode
      // label text vecome the input's value
    // else
      // Switch to .editMode
      // input value becomes the label's text

    // Toggle .editMode on the parent
}

  // Delete an existing task
var deleteTask = function() {
  console.log("delete task...");
    // When the Delete button is pressed
      // Remove the parent list item from the ul
}

  // Mark a task as complete
var taskCompleted = function() {
  console.log("task complete...");
  // Append the task list item to the #completed-tasks
  var listItem = this.parentNode;
  completedTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, incompleteTask);
}

  // Mark a task as incomplete
var incompleteTask = function() {
  console.log("task incomplete...");
  // Append the task list item to the #incompleted-tasks
  var listItem = this.parentNode;
  incompleteTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskCompleted);
}

var bindTaskEvents = function(taskListItem, checkBoxEventHandler) {
  console.log("bind list item events")
  // 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 delete button
    deleteButton.onclick = deleteTask;

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

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

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


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