Question

108

How can I verify that user name starts with a letter and contains only alphanumeric characters?

rated 0 times [ 109] [ 1] / answers: 1 / hits: 18609 / 15 Years ago, thu, august 20, 2009, 12:00:00

Currently, I have a username, what i want to validate for this username is:

Not blank

Availability

No whitespaces, I add this method:

$.validator.addMethod(nowhitespace, function(value, element) {

     return this.optional(element) || /^S+$/i.test(value);

},   No white space please);

Alphanumeric

$.validator.addMethod(alphanumeric, function(value, element) {

     return this.optional(element) || /^[a-zA-Z0-9]+$/i.test(value);

},   Alphanumeric. Only numbers and alphabet allowed);

First characters must be alphabet, cannot be numeric.

I am stuck at the last validation. How to write a regular expression to validate first character MUST be alphabet?

BTW:

The no whitespace seems having problem. I tried my script, 1 whitespace its allowed, but 2 whitespaces not allowed, why?

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

emiliotristinv

Add To Favorites

Follow

Total Points: 181

Total Questions: 99

Total Answers: 96

Location: Argentina

Member since Fri, Oct 21, 2022

2 Years ago

answered 15 Years ago blaisep · Accepted Answer

Use

/^[A-Za-z][A-Za-z0-9]+$/

for the alphanumeric method.

This matches any string which consists of a letter followed by one or more alphanumeric characters. This assumes that single character user names are not allowed. If you do want to allow single character user names, change the pattern to:

/^[A-Za-z][A-Za-z0-9]*$/

This way, there is no need for a separate check for the first character. Incidentally, this should also obviate the need for the whitespace check as a string that consists entirely of alphanumeric characters cannot contain any whitespace by definition.