Email fixed validation with regular expression in Javascript

Question

I am working on email validations using regular expressions, where I need some fixed email values to validate before proceeding

Here is a clear requirement

User can only have up to 50 character before the Octets (@) and a maximum of 25 characters after the Octets, with a total of 80 characters

I used normal regex to validate email like

let reg = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;

And now for the above requirement I am trying to create an expression like

let reg = /^\w+([\.-]?(\w{2,50})+)*@(\w{2,25})+([\.-]?\w+)*(\.\w{2,3})+$/;

But it's taking only starting character(not accepting lower than two) and not the last number of requirement, So any help would be appreciated.

Answer 1

If you want to match 1-50 word chars before the @ (so no . or -) and 1-25 word chars after the @ (also no . or -) and a total of no more than 80 chars:

^(?!.{81})(?:\w+[.-])*\w{1,50}@\w{1,25}(?:[.-]\w+)*\.\w{2,3}$

Explanation

• ^ Start of string
• (?!.{81}) Negative lookahead, assert that from the current position there are not 81 chars directly to the right
• (?:\w+[.-])* Repeat 0+ times 1+ word chars and either a . or -
• \w{1,50} Match 1-50 word chars
• @ Match literally
• \w{1,25} Match 1-25 word chars
• (?:[.-]\w+)* Repeat 0+ times matching either a . or - and 1+ word chars
• \.\w{2,3} Match a . and 2-3 word chars
• $ End of string

Regex demo