Edit Button not being created

var deleteButton=taskListItems.querySelector("button.delete"); 

var newTask=document.getElementById("new-task");
var addTaskButton=document.getElementsByTagName("button")[0];
var incompleteTaskHolder=document.getElementById("incomplete-tasks");
var completedTaskHolder=document.getElementById("completed-tasks");

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



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

    if (typeof editButton.innerText === "undefined")  {
        editButton.textContent = "Edit";
      } else {
        editButton.innerText = "Edit";
      }
    editButton.className="edit";
    editButton.className="delete";
    if (typeof deleteButton.innerText === "undefined")  {
        deleteButton.textContent = "Delete";
      } else {
        deleteButton.innerText = "Delete";
      }
    listItem.appendChild(checkBoxInput);
    listItem.appendChild(label);
    listItem.appendChild(editInput);
    listItem.appendChild(editButton);
    listItem.appendChild(deleteButton);

    return listItem;
}

var addTask=function()
{
  console.log("addTaskTriggered");
  var listItem=createNewTaskElement("Do something");

  incompleteTaskHolder.appendChild(listItem);
    bindTaskEvents(this.parentNode,taskCompleted);

}

var editTask=function()
{
console.log("edit");
}


var deleteTask=function()
{
console.log("delete");
this.parentNode.remove();
}

var taskCompleted=function()
{
    console.log("taskCompleted");
    bindTaskEvents(this.parentNode,taskIncomplete);
    completedTaskHolder.appendChild(this.parentNode);
}

var taskIncomplete=function()
{
    console.log("taskIncomplete");
    bindTaskEvents(this.parentNode,taskCompleted);
    incompleteTaskHolder.appendChild(this.parentNode);


}

var bindTaskEvents=function(taskListItems,checkBoxEventHandler)
{
    console.log("adsca");
    var checkBox=taskListItems.querySelector("input[type=checkbox]");
    var editButton=taskListItems.querySelector("button.edit");
    var deleteButton=taskListItems.querySelector("button.delete");
    editButton.onclick=editTask;
    deleteButton.onclick=deleteTask;
    checkBox.onchange=checkBoxEventHandler;
}

addTaskButton.onclick=addTask;
for (var i=0;i<incompleteTaskHolder.children.length;i++)
{
    bindTaskEvents(incompleteTaskHolder.children[i],taskCompleted);
}
for (var i=0;i<completedTaskHolder.children.length;i++)
{
    bindTaskEvents(completedTaskHolder.children[i],taskIncomplete);
}