Zhyhana,
так?
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script src="//code.jquery.com/jquery-1.11.3.min.js"></script>
<title>Быстрый переход внутри документа</title>
</head>
<body>
<form action="#" name="user-form" class="form">
<div class="wrapper_input">
<input type="text" class="input" id="company_name" name="company_name" placeholder="Компания" />
</div>
<div class="wrapper_input">
<input type="text" class="input" id="user_name" name="user_name" placeholder="Контактное лицо*" required/>
</div>
<div class="wrapper_input">
<input type="tel" class="input" id="tel"e name="tel" placeholder="Телефон*" required/>
</div>
<div class="wrapper_input">
<input type="mail" class="input" id="email"e name="email" placeholder="E-mail*" required />
</div>
<div class="wrapper_submit">
<input class="submit" type="submit" value="Отправить"/>
</div>
</form>
<script>
$('input:submit').click(function () {
$('input').each(function (i, input) {
if(!input.value.length) return;
$(input).addClass('newClass')
})
})
</script>
</body>
</html>