A JavaScript function is a block of JavaScript code, that can be executed when "called" for.
For example, a function can be called when an event occurs, like when the user clicks a button.

JavaScript in <head> or <body>

You can place any number of scripts in an HTML document.
Scripts can be placed in the <body>, or in the <head> section of an HTML page, or in both.

External JavaScript Advantages

Placing scripts in external files has some advantages:
  • It separates HTML and code
  • It makes HTML and JavaScript easier to read and maintain
  • Cached JavaScript files can speed up page loads