app.js

(function (window) { // IIFE: Immediately Invoked Function Expression
	'use strict'; // For bonus points, what does this do?

	var list = [ ];

	console.log(list);

	todos.addTaskToList("Remember the milk", list);

	console.log(list);

})(window);

todo.js

(function (window){
    var taskList = [];

    // I can list my tasks...
    function listTasks(list){
      // TODO: make this do something...
    }

    //I can add a task to my list...
    function addTaskToList(task, list){
      //What is the task?
      //Where is the task going?
      //What order / priority?
      return list.push(task);
    }

    //I can check a task off my list...
    function completeTask(task, list){
      return list[task - 1] += ' COMPLETE';
    }

    //I can delete a task off my list...
    function deleteTask(task, list){
      return list.splice(task - 1, 1);
    }

    window.todos = {
        "addTaskToList": addTaskToList,
        "completeTask": completeTask,
        "deleteTask": deleteTask
    };

})(window);