JSFiddle - React, Tailwind, and code Playground

HTML

some text

JavaScript

(function (window, document, $) {
    var getSelectedText = function () {
        var text = "";
        if (window.getSelection) {
            text = window.getSelection().toString();
        } else if (document.selection && document.selection.type != "Control") {
            text = document.selection.createRange().text;
        }
        return text;
    };
    
    $(document.body).on("mouseup", function () {
        var selectedText = getSelectedText();
        if (selectedText.length !== 0) {
            alert("You selected: " + selectedText);   
        }
    });
})(window, document, jQuery);