JSFiddle - React, Tailwind, and code Playground

by Qwerty_Wasd

HTML

<script src="//code.jquery.com/jquery-3.3.1.slim.min.js"></script>
<link rel="stylesheet" href="//stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css">
<script src="//cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.0/umd/popper.min.js"></script>
<script src="//stackpath.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<div class="form-group">
	<label class="col-sm-2 control-label" for="type_err">срочность:</label>
	<div class="col-sm-10">
		<select name="type_err" required class="form-control">
			<option  value="1">Срочная</option>
			<option selected value="2">Текущая</option>
			<option  value="3">Не срочная</option>
			<option  value="4">Без приоритета</option>
		</select>
	</div>
</div>
<div class="form-group" id="t_fin">
	<label class="col-sm-2 control-label" for="time_fin" >Срок устранения до:</label>
	<div class="col-sm-10">
		<input required type="datetime-local" class="form-control" id="time_fin" name="time_fin" placeholder="12.05.2019 12:00" />
	</div>
</div>

CSS

#t_fin {
	display: none;
}

JavaScript

$("[name='type_err']").on("change", function(){
	$("#t_fin")[(this.value === "4") ? "show" : "hide"]();
});