Update Web/JavaScript/Guide/Regular_Expressions

[mfuji09]

What was wrong/why is this fix needed? (quick summary only)

• The second exec() in "Using regular expressions in JavaScript" should be test().
• There are a lot of  s which should be normal spaces.
• Resolved some redirect links.

MDN URL of main page changed

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

[github-actions]

Preview URLs

• https://pr4847.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/JavaScript/Guide/Regular_Expressions
Title: Regular expressions
on GitHub

• Results of TC39 presentation tc39/proposal-regex-escaping#37 (1 time) (Note! This may be a new URL 👀)

[hamishwillee]

All looks good (though I can't see the problem or change made for "The second exec() in "Using regular expressions in JavaScript" should be test().").

Thanks very much!