search

tc39 / ecma262

Status, process, and documents for ECMA-262
https://tc39.es/ecma262/
Other
15.03k stars 1.28k forks source link

Octal consistently missing from definitions of numeric escape sequences #1691

Open duanemoody opened 5 years ago

duanemoody commented 5 years ago

The syntax for numeric escape systems somehow omits octal even in its \0u123 form; current implementations of Chrome and Firefox seem to assume this is an oversight and parse them in string literals. I only see documentation disallowing the deprecated legacy octal escape sequence \123 esp. in strict mode, but no explicit wholesale prohibition of octal nor a justification for such.

Editorial error?

claudepache commented 5 years ago

The following produces a Syntax Error for me in Firefox:

function x() { "use strict"; "\141" }

Note that the specific escape sequence \0 not followed by another digit is allowed, as is not considered as legacy octal escape sequence.

duanemoody commented 5 years ago

Correct, the proper encoding is \0o141 not \141 now. There is no explanation for why hex encoding is permitted but octal is not.

bathos commented 5 years ago

current implementations of Chrome and Firefox seem to assume this is an oversight and parse them in string literals

I’m not able to repro this, can you provide an example?

Edit: Since the OP didn’t mentioned strict mode, I’m guessing maybe you’re testing outside of strict mode? If so, browsers do still implement it for backwards compat. It’s currently defined in Annex B though, rather than in the main spec: https://tc39.es/ecma262/#sec-additional-syntax-string-literals.

the proper encoding is \0o141 not \141 now

The sequence "\0o141" in a string is an escaped null character followed by the literal characters "o141". This has always been true afaik. The ‘bare’ \141 syntax that used to exist is what became disallowed in strict mode — though it was actually removed by ES3, in 1999, before strict mode existed. That specific thing is was what Annex B was first introduced for, and the introductory text implies the intention at the time was deprecation (I’m guessing don’t-break-the-web was still being worked out at the time..?).

claudepache commented 5 years ago

@duanemoody I think you are confusing the syntax of some escapes in string ("\x61", "\u0061", legacy "\141") with the syntax of number literals (0x61, 0o141, legacy 0141)?