用于返回Javascript对象深处的属性值的方法的比较

考虑以下company对象：

var employee = {
    empID: 45435,
    salary: 44000,
    title: "Janitor",
    firstName: "Richard",
    lastName: "Stallman"
}

var department = {
    name: "Maintenance",
    building: "H",
    room: 404,
    departmentLead: employee
}

var company = {
    name: "Bluth's Original Frozen Banana Stand",
    revenue: 'always',
    maintenanceDept: department
}

如果我想访问该对象的title属性，则employee可以通过以下方式引用它：

var title = company.maintenanceDept.departmentLead.title;

但是，如果departmentLead为undefined，TypeError则会抛出a。因此，在访问之前，我必须编写一个测试title：

if(company && 
   company.maintenanceDept && 
   company.maintenanceDept.departmentLead &&
   company.maintenanceDept.departmentLead.title){ ... }

这是最好的方法吗？显然，此示例是人为设计的，因为我company在使用它之前就已对其进行了定义，所以我知道它是title存在的。对于company从AJAX调用返回的对象，不能说相同的话。一个解决方案我一直在使用一直以：

// Edit: I've been informed adding properties to Object.prototype is not a smart thing to do...so don't do this
Object.prototype.propertyWithPath = function (path) {
    var keys = path.split('.');
    var parent = this;
    var child;

    for (var i = 0; i < keys.length; i++) {
        child = keys[i];

        if (parent[child] === undefined) {
            return undefined;
        }
        parent = parent[child];
    }
    return parent;
};

除了性能下降外，使用这种方法与替代方法相比还有其他缺点吗？