How can I create a JavaScript regex for finding email addresses in strings?

Question

I have a logic app which is triggered by emails in an inbox. It is all working, except for some emails are getting through when I don't want them. Or rather an email signature with an image description of [email protected] is getting through. I think it might be my regex that is allowing it, but I am not very good with regex.

Here is the code I have so far:

var reg = /([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]+)/gi;
var emailData = " \n\n'[email protected]'\n\n \n\n  DevOps\n[cid:[email protected]]\n\n ";
    
//Matching email signatures
var matches = emailData .match(reg);

console.log(matches);

I need the regex to return a list of any email addresses, but they need to be fully formed. Unlike the one mentioned above which is missing the .com (or .org etc).

Your regex returns ["[email protected]", "[email protected]"], so what is the problem? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jun 22, 2021 at 13:28
based on which condition do you want to say [email protected] is not a valid email? maybe no numbers behind the last . or restrict amount of characters after last . ? — caramba
– caramba, Commented Jun 22, 2021 at 13:31
I dont want that second string, as its not an email address. I only want what looks like a valid email address. — evolmonster
– evolmonster, Commented Jun 22, 2021 at 15:25

caramba · Accepted Answer · 2021-06-22 13:52:11Z

2

Your regex (allowing everything which has an @ and a .)

const regex = /([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]+)/gm;
const str = `[email protected]
[email protected]
[email protected]
[email protected]`;
let m;

while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    console.log(m[0]);
}

#1 No numbers allowed after last .

const regex = /([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z_-]+)/gm;
const str = `[email protected]
[email protected]
[email protected]
[email protected]`;
let m;

while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    console.log(m[0]);
}

#2 Restrict characters after last . to be min 2 and max 7 characters {2,7}$

const regex = /([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9_-]{2,7}$)/gm;
const str = `[email protected]
[email protected]
[email protected]
[email protected]`;
let m;

while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    console.log(m[0]);
}

#3 Define a list of possible top-level domain names like (com|org|info)

const regex = /([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.(com|org|info)$)/gm;
const str = `[email protected]
[email protected]
[email protected]
[email protected]`;
let m;

while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    console.log(m[0])
}

edited Jun 22, 2021 at 13:52

answered Jun 22, 2021 at 13:46

caramba

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3 Comments

evolmonster Over a year ago

Thank you for the solutions! I have one problem with it, and I think its the input. I am passing in a string from a logic app step that strips out the HTML from the email, and it looks like this : var email = "[email protected]>\nSubject: FW:\n\n \n\n \n\n'[email protected]'\n\n \n\n Email Signature | Dev Team\n[cid:[email protected]]\n\n"; When I run that through my script, it comes out with no matches.

evolmonster Over a year ago

I got it. I just used replace to take out any characters I want to ignore.

caramba Over a year ago

@evolmonster the problem was most probably the $ at the end. The $ makes sure to be an end. Use this regex tool wo practice and get explanations: regex101.com/r/HCM4y7/1

dvlprkrishna · Accepted Answer · 2021-06-22 13:44:19Z

0

have a look at - https://ihateregex.io/expr/email/

Hate to break it to you but email match via Regex are hard if not impossible.

one way would be matching things with domain name TDN endings ( you can create a group of all tdn and match or just limit the end part of regex - modified regex and filter it out from there onwards.

answered Jun 22, 2021 at 13:44

dvlprkrishna

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1 Comment

evolmonster Over a year ago

This particular regex is part of an azure logic app. I read the email from the body of emails sent to a certain inbox. I figured regex/javascript would be the way to go. But if you are saying a regex wont catch everything, maybe I need another solution?

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