JSFiddle - React, Tailwind, and code Playground

HTML

<button>+</button><br><textarea></textarea>

CSS

textarea{
    display:none;
}

JavaScript

$('textarea').on('focusout', function(){
$(document).mouseup(function(){
    if(document.activeElement.tagName!=='BUTTON'){
    $('textarea').hide()
    }
})
})
$('button').click(function(){
    $('textarea').show().focus()
})