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

The approved answer from George Claghorn worked great for simply inserting text at the cursor position. If the user had selected text though, and you want that text to be replaced (the default experience with most text), you need to make a small change when setting the 'back' variable.

Also, if you don't need to support older versions of IE, modern versions support textarea.selectionStart, so you can take out all of the browser detection, and IE-specific code.

Here is a simplified version that works for Chrome and IE11 at least, and handles replacing selected text.

function insertAtCaret(areaId, text) {
    var txtarea = document.getElementById(areaId);
    var scrollPos = txtarea.scrollTop;
    var caretPos = txtarea.selectionStart;

    var front = (txtarea.value).substring(0, caretPos);
    var back = (txtarea.value).substring(txtarea.selectionEnd, txtarea.value.length);
    txtarea.value = front + text + back;
    caretPos = caretPos + text.length;
    txtarea.selectionStart = caretPos;
    txtarea.selectionEnd = caretPos;
    txtarea.focus();
    txtarea.scrollTop = scrollPos;
}