todo.js

var todoList = {
    todos: [],
    addTodo: function(todoText) {
      this.todos.push({
        todoText: todoText,
        completed: false
      });
    },
    changeTodo: function(position, todoText) {
      this.todos[position].todoText = todoText;
    },
    deleteTodo: function(position) {
      this.todos.splice(position, 1);
    },
    toggleCompleted: function(position) {
      var todo = this.todos[position];
      todo.completed = !todo.completed;
    },
    toggleAll: function() {
      var totalTodos = this.todos.length;
      var completedTodos = 0;
      
      // Get number of completed todos.
      //for (var i = 0; i < totalTodos; i++) {
       // if (this.todos[i].completed === true) {
          //completedTodos++;
      //  }
     // }
      
      this.todos.forEach (function (todo) {
        if (todo.completed === true) {
            completedTodos++;
        }
      });
      
      // Case 1: If everything’s true, make everything false.
     // if (completedTodos === totalTodos) {
        //for (var i = 0; i < totalTodos; i++) {
          //this.todos[i].completed = false;
        //}
        
       // this.todos.forEach (function (todo) {
        //  todo.completed = false;
  //});
        
      // Case 2: Otherwise, make everything true.
     // } else {
        //for (var i = 0; i < totalTodos; i++) {
        //  this.todos[i].completed = true;
          
      
      this.todos.forEach (function (todo) {
  // Case 1: If everything’s true, make everything false.
  if (completedTodos === totalTodos) {
    todo.completed = false;
  // Case 2: Otherwise, make everything true.
  } else {
    todo.completed = true;
  }
  });
  }
  };
  
  
  var handlers = {
    addTodo: function() {
      var addTodoTextInput = document.getElementById('addTodoTextInput');
      todoList.addTodo(addTodoTextInput.value);
      addTodoTextInput.value = '';
      view.displayTodos();
    },
    changeTodo: function() {
      var changeTodoPositionInput = document.getElementById('changeTodoPositionInput');
      var changeTodoTextInput = document.getElementById('changeTodoTextInput');
      todoList.changeTodo(changeTodoPositionInput.valueAsNumber, changeTodoTextInput.value);
      changeTodoPositionInput.value = '';
      changeTodoTextInput.value = '';
      view.displayTodos();
    },
    deleteTodo: function(position) {
      //var deleteTodoPositionInput = document.getElementById('deleteTodoPositionInput');
      //todoList.deleteTodo(deleteTodoPositionInput.valueAsNumber);
     // deleteTodoPositionInput.value = '';
      todoList.deleteTodo(position);
      view.displayTodos();
    },
    toggleCompleted: function() {
      var toggleCompletedPositionInput = document.getElementById('toggleCompletedPositionInput');
      todoList.toggleCompleted(toggleCompletedPositionInput.valueAsNumber);
      toggleCompletedPositionInput.value = '';
      view.displayTodos();
    },
    toggleAll: function() {
      todoList.toggleAll();
      view.displayTodos();
    }  
  };
  
  var view = {
    displayTodos: function() {
      var todosUl = document.querySelector('ul');
      todosUl.innerHTML = '';
      /*for (var i = 0; i < todoList.todos.length; i++) {
        var todoLi = document.createElement('li');
        var todo = todoList.todos[i];
        var todoTextWithCompletion = '';
  
        if (todo.completed === true) {
          todoTextWithCompletion = '(x) ' + todo.todoText;
        } else {
          todoTextWithCompletion = '( ) ' + todo.todoText;
        }
        
        todoLi.id = i;
        todoLi.textContent = todoTextWithCompletion;
        todoLi.appendChild(this.createDeleteButton())
        todosUl.appendChild(todoLi);
      }*/
      
      
      todoList.todos.forEach (function(todo,position){
        var todoLi = document.createElement('li');
        //var todo = todoList.todos[i];
        var todoTextWithCompletion = '';
  
        if (todo.completed === true) {
          todoTextWithCompletion = '(x) ' + todo.todoText;
        } else {
          todoTextWithCompletion = '( ) ' + todo.todoText;
        }
        
        todoLi.id = position;
        todoLi.textContent = todoTextWithCompletion;
        todoLi.appendChild(this.createDeleteButton())
        todosUl.appendChild(todoLi);
  
  },this);
    },
    createDeleteButton: function () {
    var deleteButton = document.createElement('button');
    deleteButton.textContent = "Delete";
    deleteButton.className = "deleteButton";
    return deleteButton;
    },
    setUpEventListeners: function (){
      var todosUl = document.querySelector('ul');
      todosUl.addEventListener ('click', function (event) {
      //get the element that was clicked on
      var elementClicked = event.target;
      //check if elementClicked is a delete button
      if (elementClicked.className === 'deleteButton') {
      handlers.deleteTodo(parseInt(elementClicked.parentNode.id));
    }
  });
  }
  };
  
  
  
   view.setUpEventListeners();