regex101: JavaScript Match Workspace

Pro

^start of line

\s*any whitespace character, repeated any number of times

Group 1(([a-zA-Z\d]+[\._])+)?

?repeats the group contents below at most once:

Group 2([a-zA-Z\d]+[\._])+

+repeats the group contents below at least once:

Character Class[a-zA-Z\d]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

\da digit

Character Class[\._]

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

Character Class[a-zA-Z\d]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

\da digit

@the literal @ (64₁₀ / 100₈ / 40₁₆)

Group 3([a-zA-Z\d]+[\.-])+

+repeats the group contents below at least once:

Character Class[a-zA-Z\d]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

\da digit

Character Class[\.-]

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[a-z]{2,3}

{2,3}matches between 2 and 3 characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

\ban ASCII word boundary

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

26 tokens

Regular Expression

^\s*(([a-zA-Z\d]+[\._])+)?[a-zA-Z\d]+@([a-zA-Z\d]+[\.-])+[a-z]{2,3}\b

New

Acceptable
---------------
hnn152151927@epu.edu.vn
postmaster@invoices.go-jek.com
xxx@yahoo.com.vn
gitlab@mg.gitlab.com
abc1.1@domain.com
abc.abc@domain.com
abc_41.15768@domain.com
12345@domain.com
12.12.23@domain.com
ABC.ABC.ABC.ABC.0046@domain.com
abc_123_4595@domain.com
abc@asdas.co.in
abc@insta123.com
abc@inta.co.in

Non-Acceptable
---------------
abc@@insta.com.com.com
abc@insta..com
abc@insta%.com
abc@insta/.com
abc@insta\\.com
abc..abc@domain.com 
abc__abc@domain.com
abc.@insta.com
abc..de@insta.com
abc-@insta.com
abc-def@insta.com
abc+@insta.com
abc123..45@insta.com
abc%@insta.com
abc\\@insta.com
abc/@insta.com
abc@insta-.com
ABC.ABC.ABC.ABC0046@domain.com.com.com

Substitution

Acceptable
---------------
hnn152151927@epu.edu.vn
postmaster@invoices.go-jek.com
xxx@yahoo.com.vn
gitlab@mg.gitlab.com
abc1.1@domain.com
abc.abc@domain.com
abc_41.15768@domain.com
12345@domain.com
12.12.23@domain.com
ABC.ABC.ABC.ABC.0046@domain.com
abc_123_4595@domain.com
abc@asdas.co.in
abc@insta123.com
abc@inta.co.in

Non-Acceptable
---------------
abc@@insta.com.com.com
abc@insta..com
abc@insta%.com
abc@insta/.com
abc@insta\\.com
abc..abc@domain.com 
abc__abc@domain.com
abc.@insta.com
abc..de@insta.com
abc-@insta.com
abc-def@insta.com
abc+@insta.com
abc123..45@insta.com
abc%@insta.com
abc\\@insta.com
abc/@insta.com
abc@insta-.com
ABC.ABC.ABC.ABC0046@domain.com.com.com