为什么for循环内部的全局变量不改变值?Javascript

我在执行一个函数时遇到了一个问题,该函数使用3个全局变量运行for循环,这些变量将被传递给回调函数。所有数组的长度都相同,问题在于3个窗口变量,称为in getPickup() 在回调函数内部,不要更改任何循环中的值。我觉得很奇怪,因为这些变量应该从中更新一个新值 location 当回调函数完成,循环再次运行时。

function calculateDistanceDriverCustomer() {
       {% autoescape off %}
       var locations = {{ locations }}
       {% endautoescape %}

       {% autoescape off %}
       var firstname = {{ firstname }}
       {% endautoescape %}

       {% autoescape off %}
       var lastname = {{ lastname }}
       {% endautoescape %}

       {% autoescape off %}
       var rating = {{ rating }}
       {% endautoescape %}
       var location;
       for (location = 0; location < locations.length; location++) {
        var origin = locations[location];
        window.firstname = firstname[location];
        window.lastname = lastname[location];
        window.rating = rating[location];
        var destination = $('#origin-input').val();
        var service = new google.maps.DistanceMatrixService();
        service.getDistanceMatrix(
                {
                    origins: [origin],
                    destinations: [destination],
                    travelMode: google.maps.TravelMode.DRIVING,
                    unitSystem: google.maps.UnitSystem.METRIC, // kilometers and meters.
                    avoidHighways: false,
                    avoidTolls: false
                }, callback);
        }
};

function callback(response, status) {
            if (status != google.maps.DistanceMatrixStatus.OK) {
                $('#result').html(err);
            } else {
                var origin = response.originAddresses[0];
                var destination = response.destinationAddresses[0];
                if (response.rows[0].elements[0].status === "ZERO_RESULTS") {
                    $('#result').html("Better get on a plane. There are no roads between "  + origin + " and " + destination);
                } else {
                        //get estimated pickup time if distance less or equal than 10km
                    function getPickup() {
                        var distance = response.rows[0].elements[0].distance;
                        var duration = response.rows[0].elements[0].duration;
                        var distance_in_kilo = distance.value / 1000;
                        var duration_value = duration.value*1000;
                        console.log(distance_in_kilo);
                        var time = new Date()
                        time = new Date(time.getTime() + duration_value);
                        var date = new Date(time)
                        var currenthr = date.getHours()
                        var currentmin = date.getMinutes()
                        var currentsec = date.getSeconds()
                        if (currenthr   < 10) {currenthr   = "0"+currenthr;}
                        if (currentmin < 10) {currentmin = "0"+currentmin;}
                        if (currentsec < 10) {currentsec = "0"+currentsec;}
                        window.pickupTime = currenthr + ":" + currentmin + ":" + currentsec;
                        console.log(pickupTime);
                        if (distance_in_kilo <= 3000) {
                            var name = document.createElement("hd");
                            var brk = document.createElement("br");
                            var node = document.createTextNode(window.firstname + " " + 
                            window.lastname);
                            name.appendChild(node);
                            var element = document.getElementById("cars");
                            element.appendChild(name);
                            element.appendChild(brk);
                            var pickup = document.createElement("hd");
                            var node1 = document.createTextNode("Pickup Time: " + window.pickupTime);
                            pickup.appendChild(node1);
                            var element1 = document.getElementById("cars");
                            element1.appendChild(pickup);
                            element1.appendChild(brk);
                            var rating = document.createElement("hd");
                            var node3 = document.createTextNode("rating: " + window.rating);
                            rating.appendChild(node3);
                            var element3 = document.getElementById("cars");
                            element3.appendChild(rating);
                            element3.appendChild(brk);
                        }
                        else {
                            console.log("Not available");
                        }

                     }
                    getPickup();
                }
            }
        };

变量是在for循环的开头定义的,它们是 window.firstname , window.lastname 和 window.rating 。它们从一个数组中获取值,该数组的内容是从python(定义于 calculateDistanceDriverCustomer() . 这是python代码:

 cursor = mysql.connection.cursor(MySQLdb.cursors.DictCursor)
    cursor.execute("SELECT CurrentLocation, FirstName, LastName, OverallRating FROM driver WHERE OnJourney=0")
    rows = cursor.fetchall()  # data from database
    locations = []
    firstname = []
    lastname = []
    rating = []
    for row in rows:
        locations.append(row['CurrentLocation'])
        firstname.append(row['FirstName'])
        lastname.append(row['LastName'])
        rating.append(row['OverallRating'])
    return render_template("Search.html", rows=rows, locations=locations, firstname=firstname, lastname=lastname, rating=rating)

谢谢你的帮助