gistfile1.js

function mouseup(evt) {
    var contentList = this.cont.list;
    var [start, end] = [contentList.indexOf(_lastItemSelected), contentList.indexOf(this)].sort();

    if (_isDD) {
        return;
    }

    if (evt.shiftKey == true) {
        for (var i = start; i <= end ; i++) {
            this.selectItem(contentList[i]);
        }
    } else {
        if (this.elem.hasClassName('mkdd-selected')) {
            this.elem.removeClassName('mkdd-selected');
        } else {
            this.selectItem(this);
        }
    }

    _lastItemSelected = this;
    this.isMouseup = true;
}