Any idea why my add item button does not add anything to list?

//Problem user interaction do not provide  results
// add interactivity so user can manage daily task

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

//new task list item
var createNewTaskElement = function(taskString){
  //create List Item
 var listItem = document.createElement("li"); 

  //input (checkbox)
  var checkBox = document.createElement("input");//input checkbox
  var label = document.createElement("label");// text

  // input (text)
  var editInput = document.createElement("input");//text
  //button.edit

  var editButton = document.createElement("button");
  //button.delete
var deleteButton = document.createElement("button");
  //Each elements, needs modifying

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

  //edit an existing task
  return listItem

}



//add a new task
var addTask = function() {
  console.log("add to Task works...");
//creat a new list item with the text from #new-task:
 var listItem = createNewTaskElement("Some New Task"); 
  //append listItem incompleteTaskholder
  incompleteTaskHolder.appendChild(listItem);

}



//Edit an existing task
var editTask = function() {
  console.log("edit task....");
  //when the edit button is pressed
  // if the class of the parend is editmode
  //switch from .editMode
  //label text bcome teh inpu valu
//else
  //seitch to editMode
  //input value becomes the labels text

//Toggle editMode on the parent

//delete an existing task

}
var deleteTask = function() {
  console.log("delete task");
  //when delete button is pressed
    //remove parrent item from ul

//mark a task as complete
}
var taskCompleted = function () {
  console.log(" taskCompleted");
     //when the checkbox is checked
     //append the task list item to the completed=tasks
     //mark a task as incomplete
     //when the checkbox is unchecked

}

var bindTaskEvents = function (taskListItem, checkBoxEventHandler) {
  console.log("Bind list item events");
    //select it'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
   //bind deleteTask to the delete button
   //bind checkBoxEventHandler to checkbox
  checkBox.onchange = checkBoxEventHandler;

}

//set event handler to addTask Function

addbutton.onclick = addTask;

//cycle over incompleteTaskHolder ul list item when checked ad to other list

   for (var i = 0; i < incompleteTaskHolder.children.length; i++) {  
//bind events to list items children (taskcompleted)
  bindTaskEvents(incompleteTaskHolder.children[i], taskCompleted);    
     }

//cycle over completedTaskHolder ul list items

   for (var i = 0; i < completeTaskHolder.children.length; i++) {  
//bind events to list items children (taskcomplete)
  bindTaskEvents(completeTaskHolder.children[i], taskIncomplete);    
     }