Any idea why none of the functionality is working for me yet?

var taskInput = document.getElementById("new-task");
var addButton = document.getElementById("button")[0];
var incompleteTasksHolder = document.getElementById("incomplete-tasks");
var completedTasksHolder = document.getElementById("completed-tasks");

var createNewTaskElement = function(taskString) {
  var listItem = document.createElement("li");
  var checkBox = document.createElement("input");
  var label = document.createElement("label");
  var editInput = document.createElement("input");
  var editButton = document.createElement("button");
  var deleteButton = document.createElement("button");

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

  return listItem;
}

// Add new task
var addTask = function() {
  console.log("Add task..."); 
  // Create a new list item with the next from #new-task:
  var listItem = createNewTaskElement("some New Task");
  // Append listItem to incompleteTasksHolder
  incompleteTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskCompleted);
}

// Edit an existing task
var editTask = function() {
  console.log("Edit task..."); 
}

// Delete an existing task
var deleteTask = function() {
  console.log("Delete task...");
}

// Mark a task complete
var taskCompleted = function() {
  console.log("Task complete...");
  var listItem = this.parentNode;
  completedTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskIncomplete);
}

// Mark a task incomplete
var taskIncomplete = function() {
  console.log("Task incomplete...");
  var listItem = this.parentNode;
  incompleteTasksHolder.appendChild(listItem);
  bindTaskEvents(listItem, taskCompleted);
}

var bindTaskEvents = function(taskListItem, checkBoxEventHandler) {
   console.log("Bind list item events...");
  var checkBox = taskListItem.querySelector("input[type=checkbox]");
  var editButton = taskListItem.querySelector("button.edit");
  var deleteButton = taskListItem.querySelector("button.delete");

  editButton.onclick = editTask;
  deleteButton.onclick = deleteTask;
  checkBox.onchange = checkBoxEventHandler;
}

addButton.onclick = addTask;

for(var i = 0; i< incompleteTasksHolder.children.length; i++) {
  bindTaskEvents(incompleteTasksHolder.children[i], taskCompleted); 
}

for(var i = 0; i< completedTasksHolder.children.length; i++) {
  bindTaskEvents(completedTasksHolder.children[i], taskCompleted); 
}