Learners can familiarize themselves with how to use Javascript in conjunction with HTML pages in this 10-video course. Explore different types of variable declarations in the language and ways in which Javascript web apps can relay info to and receive info from end-users. Key concepts covered in this course include learning how to create a simple Javascript app that writes a message to an HTML page; learning how Javascript can be used to communicate with end-users via the HTML page, alerts, and log messages; and learning how to link a HTML page with a separately defined Javascript source file. First, observe how to edit sections of a HTML page by using Javascript and initialize number and string variables; examine the changes in behavior of a Javascript app when Strict mode is enabled; and learn how to distinguish between the var, let, and const keywords when declaring variables. Finally, learn how to differentiate variables that are undefined from those whose values are null; and how to use the alert, prompt, and confirm functions to relay information to and receive input from end-users.