I can't get addButton recognized. I get an unexpected "(" message, but there's no error there. Pls advise.

//Problem: User interaction doesn't provide any of the desired results
//Solution: Add interactivity so user can complete any & all daily tasks

//All the functions need to be triggered when an event occurs on an element
//But before we trigger the event handlers, we want to select the page elements in the DOM:
var taskInput = document.getElementById("new-task"); //new-task
var addButton = document.getElementsByTagName("button")[0]; //1st button, accessed via array notation
var incompleteTasksHolder = document.getElementById("incomplete-tasks") //incomplete-tasks
var completedTasksHolder = document.getElementById("completed-tasks"); //completed-tasks

//Add new task
var addTask = function() {
  console.log("Add task...");
//when button is pressed
  //create new list item with text from #new-task
    //input (checkbox)
    //label
    //input (text)
    //button.edit
    //button.delete
    //each element needs to be modified & appended
}

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

  //When Edit button is pressed
    //if parent class is .editMode
      //switch from .editMode
      //label text becomes input's value
    //else 
      //switch to .editMode
      //input value becomes label's text

    //toggle edit mode on the parent
}

//Delete an existing task
var deleteTask = function() {
    console.log("Delete task...");
  //When Delete button is pressed
    //Remove parent list item from the ul
}

//Mark task as complete
var taskCompleted = function() {
    console.log("Complete task...");
  //when checkbox is checked
    //Append task list item to #completed-tasks
}

//Mark task as incomplete
var taskIncomplete = function() {
    console.log("Task incomplete...");
  //when checkbox is unchecked
    //Append task list item to #uncompleted-tasks
}

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