JSFiddle - React, Tailwind, and code Playground

HTML

<form action="">
  <input type="text" maxlength="13" pattern="((\+*)((0[ -]+)*|(91 )*)(\d{12}+|\d{10}+))|\d{5}([- ]*)\d{6}"  required 
name="" title="Only numbers and '+' are accepted" id="" class="register-input-val form-control input-lg" placeholder=" Mobile Number">
<button type="submit">Validate</button>  
</form>

CSS

body {
    padding: 10px;
    font-family: Arial;
    Font-size: 10pt;
}
span {
    font-weight:bold;
}