Is Node decodeURIComponent idempotent? If not, is there an idempotent alternative?-CodePudding

Is Node decodeURIComponent idempotent?

Does...

decodeURIComponent(x) === decodeURIComponent(decodeURIComponent(x))

for any and all x?

If not, is there an alternative that is idempotent? Was trying to think through if this was possible myself.

CodePudding user response：

> encodeURIComponent('%')
'%'
> encodeURIComponent(encodeURIComponent('%'))
'%25'

> decodeURIComponent('%25')
'%'
> decodeURIComponent(decodeURIComponent('%25'))
'%'

> decodeURIComponent('%25') === decodeURIComponent(decodeURIComponent('%25'))
false

CodePudding user response：

No. If the string decodes to a new sequence which itself can be interpreted as an encoded URI component, then it can be decoded again to a different string:

const x = '%21';
console.log(decodeURIComponent(x), decodeURIComponent(decodeURIComponent(x)));

%21 → ! → !

Any given string is either encoded in a specific format or is plain text. You cannot guess what it is supposed to be. ! could either be the plaintext string "!", or a URL-encoded string representing "!". You need to know which it's supposed to be and interpreted it accordingly. That generally goes for any and all text encoding formats.