Regex Cheat Sheet: 10 Patterns That Handle 90% of Real Work

Source: Dev.to

The six characters you need to know

\d  →  any digit (0-9)
\w  →  any word character (letter, digit, underscore)
\s  →  any whitespace (space, tab, newline)
\D  →  any NON-digit
\W  →  any NON-word character
\S  →  any NON-whitespace

Uppercase = inverse. That’s the whole pattern.

Quantifiers

+      one or more
*      zero or more
?      zero or one (optional)
{3}    exactly 3
{2,5}  between 2 and 5
{3,}   3 or more

The * vs + distinction matters: \d* matches an empty string (zero digits is fine). \d+ requires at least one digit. When in doubt, you want +.

The 10 patterns I copy‑paste the most

1. Email

[\w.-]+@[\w.-]+\.\w{2,}

Not RFC‑perfect. Doesn’t need to be. Handles real‑world emails.

const emails = text.match(/[\w.-]+@[\w.-]+\.\w{2,}/g);

2. URLs

https?:\/\/[\w\-._~:\/?#\[\]@!$&'()*+,;=%]+

The s? makes “s” optional; it catches both http and https.

const urls = text.match(/https?:\/\/[\w\-._~:\/?#\[\]@!$&'()*+,;=%]+/g);

3. US phone numbers

\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}

Handles 123-456-7890, (123) 456-7890, 123.456.7890, and 1234567890.

4. IP addresses (IPv4)

\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b

The \b word boundaries are important. Without them you’d match numbers inside longer strings.

5. Dates (YYYY‑MM‑DD)

\d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])

Validates format and checks month is 01‑12, day is 01‑31.

6. Hex colors

#(?:[0-9a-fA-F]{3}){1,2}\b

Matches both short #fff and long #ff00aa format.

7. Everything between double quotes

"([^"]*)"

The capture group ([^"]*) grabs the content. [^"]* means “any character except a quote, zero or more times.”

8. Whole word match

\bword\b

\b is the word‑boundary anchor. \bcat\b matches “cat” but not “catch” or “concatenate”.

9. Numbers with optional decimals

-?\d+\.?\d*

Matches 42, 3.14, -7, -0.5.

10. Multiple whitespace (for cleanup)

\s{2,}

Find two or more consecutive whitespace characters. Replace with a single space.

const clean = text.replace(/\s{2,}/g, ' ');

The three mistakes I see constantly

1. Not escaping periods. . matches ANY character. \. matches an actual period.

2. Greedy vs lazy. ".*" on the string "hello" and "world" matches "hello" and "world" (everything from the first quote to the last). Use ".*?" to match the shortest: "hello" and "world" separately.

3. Forgetting the g flag. Without it, you only get the first match. Add g for global.

// Only first match
'abc 123 def 456'.match(/\d+/);    // ["123"]

// All matches
'abc 123 def 456'.match(/\d+/g);   // ["123", "456"]

Try it live

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Full version of this cheat sheet with lookahead/lookbehind and more examples: