Facebook without JS?

Question

The mobile version of Facebook allows the site to function without JavaScript.

I have JS disabled on my Chrome Android browser.

When I try to make a comment on a post, the POST button is initially grey AND disabled; however, when I type in anything it goes blue and becomes enabled.

How is this possible without JS?

Answer 1

HTML5 validation and CSS

input:invalid {
  background-color: #ffdddd;
}

form:invalid [type="submit"] {
  background-color: #CCC;
  color: #AAA;
}

<form>
  <label>Enter a Name</label>
  <input type="text" required/>
  <br />
  <br />
  <label>Enter an email address:</label>
  <input type="email" required/>
  
  <input type="submit" />
</form>


----------

If you want it disabled, you can have two buttons and toggle their display

input:invalid {
  background-color: #ffdddd;
}

form [type="submit"][disabled] {
    display: none;
}

form:invalid [type="submit"][disabled] {
    display: inline;
}


form:invalid [type="submit"] {
  display: none;
}

<form>
  <label>Enter a Name</label>
  <input type="text" required/>
  <br />
  <br />
  <label>Enter an email address:</label>
  <input type="email" required/>
  
  <input type="submit" />
  <input type="submit" disabled="disabled" />
</form>