Toggle not working properly

//Problem: User interaction doesnt 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"); //text
   //create button.edit
   var editButton = document.createElement("button");
   //create 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.innerText = 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() {
  console.log("Add task...");
  //Create a new list item with the text from #new-task
  var listItem = createNewTaskElement(taskInput.value); 
  //append listItem to incompleteTaskHolder
  incompleteTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskCompleted);
}

//Edit an existing task
var editTask = function() {
  console.log("Edit task...")
  var listItem = this.parentNode; 
  var editInput = listItem.querySelector("input[type=text]");
  var label = listItem.querySelector("label");
  var containsClass = listItem.classList.contains("editMode");

    //if the class of the parent is .editMode
    if(containsClass) {
      //switch from .editMode
      //label text become the input's value
      label.innerText = editInput.value;
    //else
    } else {
      //switch to .editMode
      //input value becomes the label's text
      editInput.value = label.innerText;

    //toggle .editMode on the list item
      listItem.classList.toggle("editMode");
    }
}

//Delete an existing task
var deleteTask = function() {
  console.log("Delete task...")
  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() {
  console.log("Task complete...")
  //append task list item to the #completed-tasks
  var listItem = this.parentNode;
  completedTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskIncomplete);
}

//Mark a task as incomplete
var taskIncomplete = function() {
  console.log("Task incomplete...")
  //when checkbox is unchecked

    //append the task list to #incomplete-tasks
  var listItem = this.parentNode;
  incompleteTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskCompleted);
}




var bindTaskEvents = function(taskListItem, checkboxEventHandler) {
  console.log("bind list item events")
  //select its children
    var checkBox = taskListItem.querySelector("input[type=checkbox]");
    var editButton = taskListItem.querySelector("button.edit");
    var deleteButton = taskListItem.querySelector("button.delete");
    //bind the editTask to edit button
    editButton.onclick = editTask;
    //bind deleteTask to the delete button
    deleteButton.onclick = deleteTask;
    //bind checkboxEventHandler to the checkbox
    checkBox.onchange = checkboxEventHandler;
}

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

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