JSFiddle - React, Tailwind, and code Playground

HTML

<select name="drop1" id="Select1">
    <option value="1">choix 1</option>
    <option value="2">choix 2</option>
    <option value="3">choix 3</option>
</select>
<div class="div" id="d1">Formulaire 1</div>
<div class="div" id="d2">Formulaire 2</div>
<div class="div" id="d3">Formulaire 3</div>

JavaScript

$(".div").hide();

$("#Select1").change(function (select) {

    var index = $(this).val();

    $(".div").hide();
    $("#d" + index).show();


});