JSFiddle - React, Tailwind, and code Playground

HTML

<td> <span id="MainContent_GridView1_lblCustID_1">8</span>

</td>
<td> <span id="MainContent_GridView1_lblFirstName_1">Deborah</span>

</td>
<td> <span id="MainContent_GridView1_lblLastName_1">Damien</span>

</td>
<td> <span id="MainContent_GridView1_lblCity_1">Fresno</span>

</td>
<td>
    <input name="ctl00$MainContent$GridView1$ctl03$txtEmail" type="text" value="[email protected]" id="MainContent_GridView1_txtEmail_1" /> <span data-val-controltovalidate="MainContent_GridView1_txtEmail_1" data-val-errormessage="Must enter Email Address" data-val-validationGroup="grpEmail" id="MainContent_GridView1_ctl00_1" data-val="true" data-val-evaluationfunction="RequiredFieldValidatorEvaluateIsValid" data-val-initialvalue="" style="visibility:hidden;">Must enter Email Address</span>

    <input type="submit" name="ctl00$MainContent$GridView1$ctl03$btnUpdate" value="Update Email" onclick="return validateEmail(this);" id="MainContent_GridView1_btnUpdate_1" ButtonType="Button" />
</td>

JavaScript

function validateEmail(btnObj) {            
      alert(btnObj.id);
      var email = $(btnObj).siblings('input:text').attr('id');
      alert(email);
      return false;
  }