Javascript refactoring

gistfile1.js

function mouseup(evt) {
    if (_isDD) {
        return;
    }
    if (evt.shiftKey == true) {
        var indexOf1 = this.cont.list.indexOf(_lastItemSelected);
        var indexOf2 = this.cont.list.indexOf(this);
  
        for (var i = indexOf2; i > indexOf1; i--) {
            var item = this.cont.list[i];
            if (!item.elem.hasClassName('mkdd-selected')) {
                this.selectItem(item);
            } else {
                break;
            }
        }

        for (var j = indexOf2; j < indexOf1 ; j++) {
            var item = this.cont.list[j];
            if (!item.elem.hasClassName('mkdd-selected')) {
                this.selectItem(item);
            } else {
                break;
            }
        }

    } else {
        if (this.elem.hasClassName('mkdd-selected')) {
            this.elem.removeClassName('mkdd-selected');
        }
        else {
            this.selectItem(this);
        }
    }
    _lastItemSelected = this;
    this.isMouseup = true;
}

Questa è la mia:

function selectElement(item){
    if (item.elem.hasClassName('mkdd-selected')) {
        return false;
    } else {
        this.elem.addClassName('mkdd-selected');
    }
    return true;
}

function loopFor(startIndex, endIndex){
    for (var i = startIndex; i < endIndex; i++) {
        var item = this.cont.list[i];
        if (!selectElement(item)){
            break;
        }
    }
}

function mouseup(evt) {
    if (_isDD) {
        return;
    }
    if (evt.shiftKey == true) {
        var indexOf1 = this.cont.list.indexOf(_lastItemSelected);
        var indexOf2 = this.cont.list.indexOf(this);

        loopFor(indexOf1 - 1, indexOf2 + 1);
        loopFor(indexOf2, indexOf1);

    } else {
        if (!selectElement(item)){
            this.elem.removeClassName('mkdd-selected');
        }
    }
    _lastItemSelected = this;
    this.isMouseup = true;
}