JSFiddle - React, Tailwind, and code Playground

HTML

<form name="registr" >
		<li>Имя<span>*</span> <input type="text" name="name" maxlength="10" required><span class="trfl"></span></li>
		<li>Фамилия<span>*</span> <input type="text" name="name" maxlength="15" required></li>
		<li>Город<span>*</span> <input type="text" name="name" size="20" maxlength="20" required></li>
		<br>
		<li>E-mail<span>*</span> <input type="text" name="email" required></li>
		<li>Пароль<span>*</span> <input type="password" name="pass" maxlength="15" required></li>
		<li>Повторите пароль<span>*</span> <input type="password" name="pass" maxlength="15" required></li>
		<br>
		<input type="button" name="form" value="Регистрация" class="butt" onclick="proverka(registr);">
		<input type="reset" name="form" value="Стереть" class="butt"onclick="reset(registr);" > 
	</form>

CSS

form {
	border: 1px solid silver;
	border-radius: 5px;
	padding: 10px;
	width: 400px;
	height: 250px;
	margin: 50px auto;
	font: 16px Calibri;
}

li {
	list-style: none;
	padding: 5px;
}

input {
	float: right;
	margin-right: 20px;
}

span {
	color: red;
	font: 12px Tahoma;
	font-weight: bold;
}

.butt {
	float: left;
	margin-right: 10px;
	padding: 1px;
}

JavaScript

function proverka(obj){
	var a = obj.name.value;
	var b = obj.email.value;
	var c = obj.pass.value;
	// ........
	console.log( a );
	console.log( b );
	console.log( c );
	// ........
	var a_pattern = /^[а-яa-z ]+$/i;
	var b_pattern = /^.+@.+\..+$/i;
	var c_pattern = /^[0-9a-z]+$/i;
	var prov = a_pattern.test(a);
	var prov1 = b_pattern.test(b);
	var prov2 = c_pattern.test(c);
	if (prov==true && prov1==true && prov2==true) {
		$(".trfl").html("<span>&#10004;</span>");
	}
	else {
		$(".trfl").html("<span>&#10006;</span>");
	}
}