Keypress in jQuery: Press TAB inside TEXTAREA (when editing an existing text)

Question

I want to insert TAB characters inside a TEXTAREA, like this:

{KEYPRESS-INSERTS-TAB-HERE}Hello World

I can

Answer 1

Yeah, dealing with input field selections across the different browsers is an annoyance, especially as in IE there are a few methods that look like they should work but actually don't. (Notably, combining using setEndPoint then measuring length, which looks OK until the selection starts or ends in newlines.)

Here's a couple of utility functions I use to deal with input selections. It returns the value of the input split into bits that are before, inside and after the selection (with the selection counting as an empty string at the input focus position if it's not a selection). This makes it fairly simply to replace and insert content at the point you want, whilst taking care of the IE CRLF problem.

(There may be a jQuery that does something like this, but I have yet to meet one.)

// getPartitionedValue: for an input/textarea, return the value text, split into
// an array of [before-selection, selection, after-selection] strings.
//
function getPartitionedValue(input) {
    var value= input.value;
    var start= input.value.length;
    var end= start;
    if (input.selectionStart!==undefined) {
        start= input.selectionStart;
        end= input.selectionEnd;
    } else if (document.selection!==undefined) {
        value= value.split('\r').join('');
        start=end= value.length;
        var range= document.selection.createRange();
        if (range.parentElement()===input) {
            var start= -range.moveStart('character', -10000000);
            var end= -range.moveEnd('character', -10000000);
            range.moveToElementText(input);
            var error= -range.moveStart('character', -10000000);
            start-= error;
            end-= error;
        }
    }
    return [
        value.substring(0, start),
        value.substring(start, end),
        value.substring(end)
    ];
}

// setPartitionedValue: set the value text and selected region in an input/
// textarea.
//
function setPartitionedValue(input, value) {
    var oldtop= input.scrollTop!==undefined? input.scrollTop : null;
    input.value= value.join('');
    input.focus();
    var start= value[0].length;
    var end= value[0].length+value[1].length;
    if (input.selectionStart!==undefined) {
        input.selectionStart= start;
        input.selectionEnd= end;
        if (oldtop!==null)
            input.scrollTop= oldtop;
    }
    else if (document.selection!==undefined) {
        var range= input.createTextRange();
        range.collapse(true);
        range.moveEnd('character', end);
        range.moveStart('character', start);
        range.select();
    }
}