JSFiddle - React, Tailwind, and code Playground

HTML

<dl>
    <dd>
        <input class='str1' onkeyup='copyTulisan()' />
    </dd>
    <dd>
        <input class='str2' />
    </dd>
    <dd>
        <input type=button onclick='copyTulisan()' value='klik buat melihat perubahan' />
    </dd>
</dl>

JavaScript

function copyTulisan() {
    $s1 = $(".str1").val();
    $(".str2").val($s1);
}