What is the purpose of global keyword in javascript comments

Question

I have noticed that some javascript files have comments at the top like this:

/* global Blob */
/* global MediaRecorder */
/* global MediaSource */
/* global URL */

What is the purpose of this?

Answer 1

They are used for linters (like JSHint).

Denoting them as a global tells the linter not to complain when it finds it later on in the file. It tells it that it's defined elsewhere.