How to convert C# regex to typescript regex?

Question

I am new to angular, i have the c# email regex and i don't know what is the difference between the c# regex and typescript regex. it's not working properly.Thanks in advance

Regex:

EmailRegularExpresssion = @"^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z-])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$";

Example Email: adasd457@sdjf45.idie

1.Don't allow special character

2.don't allow number after . value(ex-sdf@sadf.co333)

It's very difficult to help you without example inputs on which the expression fails. — Dan Wilson, Sep 12 '18 at 14:58
Can you be more specific than "i not working properly"? For example, strings that you think the regex should accept, but which aren't accepted, or vice versa? And any attempts you've already made (if any) on figuring out what's wrong? — , Sep 12 '18 at 14:58
If you are trying to validate an email, `angular` has an internal directive that do the job for you anyway — Jacopo Sciampi, Sep 12 '18 at 15:04
Your regex doesn't allow for + user part of the e-mail address. It's a valid character, as are many others. — ProgrammingLlama, Sep 12 '18 at 15:10
If you're asking how that exact regex is written in JavaScript, it's just `/^([\da-z]([-.\w]*[\da-z-])*@([\da-z][-\w]*[\da-z]\.)+[a-z]{2,9})$/i` — Patrick Roberts, Sep 12 '18 at 15:11

score 3 · Accepted Answer · edited Sep 12 '18 at 15:35

3

The C# code you've provided uses C#'s Verbatim string syntax, which doesn't require escaping of backslashes. To convert it to a normal string literal, which would be the same in C# and JavaScript, you can remove the @ symbol at the front and then escape backslashes by adding another backslash before them:

 "^([0-9a-zA-Z]([-.\\w]*[0-9a-zA-Z-])*@([0-9a-zA-Z][-\\w]*[0-9a-zA-Z]\\.)+[a-zA-Z]{2,9})$"

To use this as a JavaScript Regex, you pass it to the RegExp constructor:

let emailRegularExpression = new RegExp("^([0-9a-zA-Z]([-.\\w]*[0-9a-zA-Z-])*@([0-9a-zA-Z][-\\w]*[0-9a-zA-Z]\\.)+[a-zA-Z]{2,9})$");

Or, even better, you can just use JavaScript's literal regex syntax (without escaping backslashes:

let emailRegularExpression = /^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z-])*@([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$/;

This works as specified for the cases you've specified:

emailRegularExpression.test("adasd457@sdjf45.idie"): true
emailRegularExpression.test("ex-sdf@sadf.co333"): false
emailRegularExpression.test("j²coolio@sadf.co333"): false (special character)

edited Sep 12 '18 at 15:35

Patrick Roberts

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answered Sep 12 '18 at 15:21

StriplingWarrior

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Don't use the `RegExp` constructor, it recompiles the regular expression every time that line is invoked whereas a `RegExp` literal like [here](https://stackoverflow.com/questions/52298131/how-to-convert-c-sharp-regex-to-typescript-regex?noredirect=1#comment91544552_52298131) will be statically compiled. – Patrick Roberts Sep 12 '18 at 15:23
@PatrickRoberts: Thanks for pointing that out. I updated my answer. – StriplingWarrior Sep 12 '18 at 15:25
this regex is valid : `^(?=\P{Ll}*\p{Ll})(?=\P{Lu}*\p{Lu})(?=\P{N}*\p{N})(?=[\p{L}\p{N}]*[^\p{L}\p{N}])[\s\S]{8,}$` but when inserted between two `/` it breaks syntax. wheras your example doesn't. EDIT it seems I have to double the \ – tatsu Feb 22 '21 at 22:01

How to convert C# regex to typescript regex?

1 Answers1