Hello Reader's! If you want to show what the text user has selected in a alert box, Then by using Javascript you can perform this task very quickly.

Step1:-

<div>Some test text for you to select</div> 

Make a div that shows the text.

Now write the JS as follows:-

function getSelectedText() {
    var text = "";
    if (typeof window.getSelection != "undefined") {
        text = window.getSelection().toString();
    } else if (typeof document.selection != "undefined" && document.selection.type == "Text") {
        text = document.selection.createRange().text;
    }
    return text;
}

function doSomethingWithSelectedText() {
    var selectedText = getSelectedText();
    if (selectedText) {
        alert("Got selected text " + selectedText);
    }
}

document.onmouseup = doSomethingWithSelectedText;
document.onkeyup = doSomethingWithSelectedText;

Now what ever user will select the text, it will be shown in alert box