JSFiddle - React, Tailwind, and code Playground

HTML

<select id="sendFeedbackList" name="reason" style="width:30%;">
        <option value="1">send feedback</option>
        <option value="2">report an issue</option>
        <option value="3">propose idea</option>
        <option value="4">other</option>
    </select>
    </label>
    <label><span style='font-weight: bold;'>Reason:</span>
    </label>
    <textarea form="input" id="txtarea" placeholder="Write your reason here..." name="reason_other" cols="28" rows="5"></textarea>
    <div style="text-align:right;"><span style="font-weight:bold;" id="counter"></span>
    </div>
    <input type="submit" value="Submit">

JavaScript

$("#txtarea").hide();
$( "#sendFeedbackList" ).change(function() {
  var val = $("#sendFeedbackList").val();
    if(val=="3"){
        $("#txtarea").show();
    } else {
                $("#txtarea").hide();
    }
});