js 光标位置

1，firefox 富文本编辑框中

        var range = document.createRange();
        range.selectNodeContents(obj);
        range.collapse(false);
        var sel = window.getSelection();
        sel.removeAllRanges();
        sel.addRange(range);

 2，input或textarea中

	if (document.selection) {
            var sel = obj.createTextRange();
            sel.moveStart('character',s.length);
            sel.collapse(true);
            sel.select();
        } else if (typeof obj.selectionStart == 'number' && typeof obj.selectionEnd == 'number') {
            obj.selectionStart = obj.selectionEnd = s.lenght;
        }