Alf’s blog about geek stuffs

I was looking for a javascript which could automatically resize a textarea but the ones I’ve found were a bit buggy or ugly, so I’ve written mine. There’s just a tiny bug with copy/paste with mouse.

function autoresize(txtbox)
{
    var cols = txtbox.cols ;
    var content = txtbox.value ;
    var lineCount = 0 ;

    var lastEOL = -1 ;
    do {
        var begin = lastEOL+1 ;
        lastEOL = content.indexOf("\n",lastEOL+1) ;
        var line = "" ;
        if(lastEOL != -1) {
            line = content.substring(begin,lastEOL) ;
        } else {
            line = content.substring(begin,content.length) ;
        }
        var rows_in_line = Math.floor(line.length/cols)+1 ;
        lineCount += rows_in_line
    } while (lastEOL != -1) ;
    txtbox.rows = lineCount ;
}

and html code :

<textarea name="my_textbox" onkeyup="autoresize(this)"
onmouseup="autoresize(this)" rows="24" cols="80"></textarea>