JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="textarea-1"></textarea>
<a href="#" id="link-1" style="display:none">Link</a>

JavaScript

$('#textarea-1').on('keyup', function(e){
    if($(this).val() == 'parola_chiave')
        $('#link-1').show();
    else
        $('#link-1').hide();
});