Text-input not transferred after hitting Add-button: Todo-list problem

// 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"); 
var completedTasksHolder = document.getElementById("completed-tasks");


//New Task Li

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
        //button.edit
    var editButton = document.createElement("button");
        //button.delete
    var deleteButton = document.createElement("button");
        //Each element needs modifying and appending

    checkBox.type = "checkbox";
    editInput.type = "text";

    editButton.innerText = "Edit";
    editButton.className = "edit";
    deleteButton.innerText = "Delete";
    deleteButton.className = "delete";

    label.innerText = taskString;


    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 li to incompleteTasksHolder
incompleteTasksHolder.appendChild(listItem);
    bindTaskEvents(listItem, taskCompleted);


}


// edit 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 become the input's value
        //else 
            //switch to .editMode
            //input value becomes the label's text
}

// delete existing task

var deleteTask = function () {
    console.log("delete task...");


    var listItem = this.parentNode;
    var ul =listItem.parentNode;
            //remove the parent li from the ul
    ul.removeChild(listItem);
}    

//mark task as complete

var taskCompleted = function () {
    console.log("task Complete...");
   //append the task li to the #completed-tasks
   var listItem = this.parentNode;
    completedTasksHolder.appendChild(listItem);
    bindTaskEvents(listItem, taskIncomplete);
}

//mark task as incomplete

var taskIncomplete = function () {
    console.log("task Incomplete...");
    //append the task li to the #incomplete-tasks
    var listItem = this.parentNode;
    incompleteTasksHolder.appendChild(listItem);
    bindTaskEvents(listItem, taskCompleted);
}

var bindTaskEvents = function (taskListItem, checkBoxEventHandler) {
   console.log("bind li 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 checkBoxEventHandler the checkbox
    checkBox.onchange = checkBoxEventHandler;
}


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

//cycle over incompleteTasksHolder ul list items
for ( i = 0; i < incompleteTasksHolder.children.length; i++ ){

    //bind events to list item's children (taskCompleted)
    bindTaskEvents(incompleteTasksHolder.children[i], taskCompleted);
        }

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