"Uncaught Typeerror: Cannot read property 'querySelector of undefined"

//Problem: User interaction doesn't provide desired results.
//Solution: Add user interactivity so the suer 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

//Add a new task
var addTask = function() {
  console.log("Add task...")
  //When the button is pressed 
  //Create a new list item with the text from the #new-task:
    //input checkbox
    //label
    //input (text)
    //button.edit
    //button.delete
    //Each elements, need modified and appended
}

//Edit an existing task
var editTask = function() {
  console.log("Add task...")
  //When the Edit button is pressed 
   //if the class of the parent is .editMode
      //Switch from .editMode
      //label text become thge 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("Add 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("Add task...")
  //When the Checkbox is checked
    //Append the task list item to the #completed-task
}

//Mark a task as incomplete
var taskIncomplete = function() {
  console.log("Add task...")
  //When the Checkbox is unchecked
    //Append the task list item to the #incompleted-task
}


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.onlcick = editTask;

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

    //bind checkBoxEventHandler to the checkbox
    checkBox.change = checkBoxEventHandler;


}

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


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

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