How do I add text to a textarea at the cursor location using javascript [duplicate]

Answer 1

It's a bit tricky in IE, which does an exceptionally bad job of this kind of thing. The following will insert text at the end of the current selection in a textarea or text input (or at the caret if the no text is selected) and then position the cursor after the text:

Demo: http://jsfiddle.net/RqTvT/1/

Code:

function getInputSelection(el) {
    var start = 0, end = 0, normalizedValue, range,
        textInputRange, len, endRange;

    if (typeof el.selectionStart == "number" && typeof el.selectionEnd == "number") {
        start = el.selectionStart;
        end = el.selectionEnd;
    } else {
        range = document.selection.createRange();

        if (range && range.parentElement() == el) {
            len = el.value.length;
            normalizedValue = el.value.replace(/\r\n/g, "\n");

            // Create a working TextRange that lives only in the input
            textInputRange = el.createTextRange();
            textInputRange.moveToBookmark(range.getBookmark());

            // Check if the start and end of the selection are at the very end
            // of the input, since moveStart/moveEnd doesn't return what we want
            // in those cases
            endRange = el.createTextRange();
            endRange.collapse(false);

            if (textInputRange.compareEndPoints("StartToEnd", endRange) > -1) {
                start = end = len;
            } else {
                start = -textInputRange.moveStart("character", -len);
                start += normalizedValue.slice(0, start).split("\n").length - 1;

                if (textInputRange.compareEndPoints("EndToEnd", endRange) > -1) {
                    end = len;
                } else {
                    end = -textInputRange.moveEnd("character", -len);
                    end += normalizedValue.slice(0, end).split("\n").length - 1;
                }
            }
        }
    }

    return {
        start: start,
        end: end
    };
}

function offsetToRangeCharacterMove(el, offset) {
    return offset - (el.value.slice(0, offset).split("\r\n").length - 1);
}

function setSelection(el, start, end) {
    if (typeof el.selectionStart == "number" && typeof el.selectionEnd == "number") {
        el.selectionStart = start;
        el.selectionEnd = end;
    } else if (typeof el.createTextRange != "undefined") {
        var range = el.createTextRange();
        var startCharMove = offsetToRangeCharacterMove(el, start);
        range.collapse(true);
        if (start == end) {
            range.move("character", startCharMove);
        } else {
            range.moveEnd("character", offsetToRangeCharacterMove(el, end));
            range.moveStart("character", startCharMove);
        }
        range.select();
    }
}

function insertTextAtCaret(el, text) {
    var pos = getInputSelection(el).end;
    var newPos = pos + text.length;
    var val = el.value;
    el.value = val.slice(0, pos) + text + val.slice(pos);
    setSelection(el, newPos, newPos);
}

var textarea = document.getElementById("your_textarea");
insertTextAtCaret(textarea, "[INSERTED]");