What does "assert" means in javascript ?

Answer 1

allows you to test your code.

https://docs.oracle.com/javase/8/docs/technotes/guides/language/assert.html

Answer 2

@jay:
Your link is for Java 8, and the question is tagged 'javascript' ;)

Anyway, that's change not a lot the meaning... but 'assert' seems not to be a standard function, exept as method of 'console' object, and in node.js.
However, this can also be a custom function from a library ^^