`atob` should throw an error if the input is not correctly encoded

[zloirock]

Version

17.9.0

Platform

MacOS 12.2

Subsystem

global / buffer

What steps will reproduce the bug?

No response

How often does it reproduce? Is there a required condition?

No response

What is the expected behavior?

atob('a') // => DOMException
atob('a ') // => DOMException
atob('aaaaa') // => DOMException

What do you see instead?

atob('a') === ''
atob('a ') === ''
atob('aaaaa') === 'i¦\x9A'

Additional information

https://infra.spec.whatwg.org/#forgiving-base64-decode step 3

Related to #42539 / #42530 @aduh95

[austinkelleher]

I'd be happy to take a look at this one and open a PR!

[aduh95]

Thanks for volunteering @austinkelleher, PR’s welcome :)