JSFiddle - React, Tailwind, and code Playground
HTML
<input type="submit" onclick="this.disabled=true;this.value='Sending, please wait...';this.form.submit();" name="btnSubmit" id="btnSubmit" value="Submit" />
<input type="submit" onclick="this.disabled=true;this.value='Sending, please wait...';this.form.submit();" name="btnSubmit" id="btnSubmit" value="Submit" />