Nsryjdtyk

HTML

<div class="top-section" style="" xpath="1">

         <input id="role" value="admin" hidden="">

            <small>Welcome </small> <b style="">8828024404, MCGM</b>

            <a href=""><img alt="Attendance" width="" height="" src="css/assets/images/logo.png"></img></a>

            <a href="/logout" class="float-right logout">Log Out</a>

        </input>

</div>

String to search

8828024404, MCGM

Xpath Expression

//b[matches(text(),'[0-9]{10}, [A-Za-z]*')]

Exception

org.openqa.selenium.InvalidSelectorException: invalid selector: Unable
to locate an element with the xpath expression
//b[matches(text(),'[0-9]{10}, [A-Za-z]')] because of the following
error: SyntaxError: Failed to execute 'evaluate' on 'Document': The
string '//b[matches(text(),'[0-9]{10}, [A-Za-z]')]' is not a valid
XPath expression. (Session info: chrome=70.0.3538.102) (Driver
info: chromedriver=2.42.591088
(7b2b2dca23cca0862f674758c9a3933e685c27d5),platform=Windows NT
10.0.16299 x86_64) (WARNING: The server did not provide any stacktrace information) Command duration or timeout: 0 milliseconds

Selenium supports XPath 1.0 version while fn:matches is from XPath 2.0.

If you want to match bold text that starts with 10 digits before comma, you can try below XPath

//b[string-length(substring-before(., ','))=10 and number(substring-before(., ','))]

Let me know in case you have more constraints to required element

Quite not sure about your exact usecase why you want a xpath to search for a Regex.

However the resultant text seems to be a part of the Welcome Message and I feel your usecase may be to extract the text which will be dynamic e.g. 8828024404, MCGM.

In this case you can use either of the following solutions:

• 
  

  XPath 1:

  
  
  

  //div[@class='top-section']/input[@id='role' and @value='admin']//b
  
  

  
  


• 
  

  XPath 2:

  
  
  

  //div[@class='top-section']/input[@id='role' and @value='admin']/small[contains(.,'Welcome')]//following::b[1]