Isabella Di Fabio Secret Story: The essence of JS Injection is to inject Javascript code that is executed on the client side. This method is probably the oldest method of Javascript injection, and it is the method we mainly use. When a user enters a piece of Javascript code on your site, it is usually in the form of Javascript that is entered into the address bar itself. Line of Code Injection is a method used mainly in web applications such as websites, mobile applications and mobile apps.