JSFiddle - React, Tailwind, and code Playground

HTML

<div id="signup">
    <form action="" method="POST" id="form1">
        <input name="user" type="text" placeholder="Username" size="30" class="signup_txt">
        <input name="pass" type="password" placeholder="Password" size="30" class="signup_txt">
        <input class="btn" type="submit" value="sign up" name="signup" id="signup_btn">
    </form>
</div>

CSS

.signup_txt{
    display:none;
}

JavaScript

$("#signup_btn").click(function(){
      $(".signup_txt").show(); 
});