wwwebman/add-remove-input-class.js

## add-remove-input-class.js
var IputEffect = function(){
    var placeholderPosition, appendInputWhenSelect, actions;


    actions = {
        activate: function(el) {
            el.parentNode.parentNode.addClass('active');
        },
        deactivate: function(el) {
            if (el.value === '') el.parentNode.parentNode.removeClass('active');
        }
    };

    placeholderPosition = function (el) {
        if (el.value !== '') actions.activate(el);
        el.addEventListener('focus', function(){actions.activate(this)});
        el.addEventListener('blur', function(){actions.deactivate(this)});
    }

    document.querySelectorAll('.js_int').forEach(function(el){
        placeholderPosition(el);
    })
}

IputEffect();

## index.html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
<div class="input-item">
    <span><input type="tel" name="d1" value="" class="int js_int"></span>
    <label>Data</label>
</div>
</body>
</html>

## input.scss
int {
  background-color: transparent;
  background-image: none; // Reset unusual Firefox-on-Android default style; see https://github.com/necolas/normalize.css/issues/214
  border-radius: 0;
  border: 0;
  border-bottom: 1px solid  #333;
  color: #555;
  display: block;
  padding: 10px;
  font-size: 16px;
  line-height: 1;
  transition: all .3s;
  width: 100%;
  outline: none;
}

.input-item {
  position: relative;
  margin-bottom: 30px;
  label {
    font-size: .9em;
    transition: all 0.35s;
    pointer-events: none;
    top: .4em;
    position: absolute;
    user-select: none;
    color: #555;
    padding: 8px 15px;
  }
  &.active {
    label {
      top: -1.75em;
      color: #000;
      font-size: .75em;
    }
  }
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<title>Document</title>
	</head>
	<body>
	<div class="input-item">
	<span><input type="tel" name="d1" value="" class="int js_int"></span>
	<label>Data</label>
	</div>
	</body>
	</html>
	int {
	background-color: transparent;
	background-image: none; // Reset unusual Firefox-on-Android default style; see https://github.com/necolas/normalize.css/issues/214
	border-radius: 0;
	border: 0;
	border-bottom: 1px solid #333;
	color: #555;
	display: block;
	padding: 10px;
	font-size: 16px;
	line-height: 1;
	transition: all .3s;
	width: 100%;
	outline: none;
	}

	.input-item {
	position: relative;
	margin-bottom: 30px;
	label {
	font-size: .9em;
	transition: all 0.35s;
	pointer-events: none;
	top: .4em;
	position: absolute;
	user-select: none;
	color: #555;
	padding: 8px 15px;
	}
	&.active {
	label {
	top: -1.75em;
	color: #000;
	font-size: .75em;
	}
	}