What does $$ in javascript of Magento 2 mean?

Question

In some core Magento modules I see the $$ signs used constantly when selecting an element. For example, in just 10 lines of code I have the following different selectors:

1. $('selection-apparently-a-custom-element')

2. $$('#some-element-id')

3. jQuery('#another-element-id')

What is the point of this?

Answer 1

There is still some prototype.js left over from Magento 1, now mixed with jQuery (in noConflict mode)

That means:

• $ is the prototype selector that returns one element by its id
• $$ is the prototype selector that returns an array of elements by CSS selector
• jQuery is what would be $ in a pure jQuery environment and returns a jQuery wrapper for an element by CSS selector