Inserting a text where cursor is using Javascript/jquery

Question

I have a page with a lot of textboxes. When someone clicks a link, i want a word or two to be inserted where the cursor is, or appended to the textbox which has the focus.<

Answer 1

Maybe a shorter version, would be easier to understand?

    jQuery("#btn").on('click', function() {
        var $txt = jQuery("#txt");
        var caretPos = $txt[0].selectionStart;
        var textAreaTxt = $txt.val();
        var txtToAdd = "stuff";
        $txt.val(textAreaTxt.substring(0, caretPos) + txtToAdd + textAreaTxt.substring(caretPos) );
    });

There is some text here.

I wrote this in response to How to add a text to a textbox from the current position of the pointer with jquery?