JSFiddle - React, Tailwind, and code Playground

HTML

<div class="loginForm">
		<input class="input jmeno" type="text" name="jmeno" placeholder="jmeno" value=""><br>
		<div id="input_container"><input class="input heslo" type="text" name="heslo" placeholder="heslo" value="">
		<img src="https://www.w3.org/2005/ajar/icons/16dot-blue.gif" id="input-blue-img">
    <img src="http://www.berrylocate.com/images/dotgreen.png" id="input-green-img">
		</div>
	
	</div>

CSS

#input-green-img {
  display:none;
}

JavaScript

var $allInputs = $("input:text"),
    $button = $("#input-blue-img");
$button2 = $("#input-green-img");
$allInputs.change(function(){
    var isEmpty = $allInputs.filter(function(){
                  return ($(this).val()=="");
              });
    $button.hide();
    $button2.show();
    if(isEmpty.length == 0){
        $button.show();
    }
});