javascript.info The Modern JavaScript Tutorial Part 2: 2.4 Browser default actions by Ilya Kantor
Youtube by Lisa Friedrichsen
This youtube explores the use of the preventDefault() method of an event object to override the default action of a browser such as loading a new web page when you click a hyperlink or displaying the default shortcut menu when you right-click a blank area of a web page.
It uses an image gallery example with hyperlinked thumbnail images that when clicked, load a larger image instead of opening a new web page with the larger image.

Original source