Most modern websites use some sort of server engine to generate the HTML for their web pages. If you are familiar with the Microsoft stack of technologies, then you would know that ASP.NET MVC is a very popular server-side engine, used to generate HTML pages based on master pages, partial pages, and MVC views. If you are a Node developer, then you may be using one of the popular Node packages to help you construct web pages through templates, such as Jade, Handlebars, or Embedded JavaScript (EJS).
Within these templating engines, you may sometimes need to set JavaScript properties on the HTML page as a result of your server-side logic. As an example, let's assume that you keep a list of contact email addresses on your database, and then surface these to your HTML page through a JavaScript global variable named CONTACT_EMAIL_ARRAY. Your rendered HTML page...