Regex in 10 Minutes: The Patterns You'll Actually Use

Email

/^[^@\s]+@[^@\s]+\.[^@\s]+$/ — not RFC-perfect, but catches 99.9% of real emails and rejects obvious junk.

Do not try to write a fully RFC-compliant email regex. It is 6,000+ characters long and you will never need it.

URL

/^https?:\/\/[^\s/$.?#].[^\s]*$/ — matches http and https URLs with a host and optional path.

For full validation, use the URL constructor in JavaScript: new URL(input) throws on invalid URLs.

Whitespace and trimming

/\s+/g matches any run of whitespace. Combine with .replace() to collapse multiple spaces into one.

/^\s+|\s+$/g trims leading and trailing whitespace, but String.prototype.trim() is faster and more readable.

Tester workflow

Always test regex in a tester (we ship one) before pasting into production code. Use real sample inputs, including edge cases.

Test for false positives as much as for matches. A regex that matches too much is worse than one that matches too little.