JSFiddle - React, Tailwind, and code Playground

HTML

<p>Press ,, </p>
<textarea></textarea>

JavaScript

$("textarea").bind("keyup", function() {
    var cursorPosition = $('textarea').prop("selectionStart");
    var text = $(this).val();
    if (text.indexOf(',,') > -1) {
        text = text.replace(/,,/g, "′");
        $(this).val(text);
        $('textarea').prop("selectionStart", cursorPosition - 1);
        $('textarea').prop("selectionEnd", cursorPosition - 1);
    }
});