Question

当我使用DirectionService将坐标放入折线时... 我意识到，回调函数外部的可变折线根本没有改变。我也尝试了变量x ..它是一样的.. 我只想要这个代码工作.. 无论如何，当回调范围发生变化时，变量外部回调会发生变化吗？

var polyline = new google.maps.Polyline({
    path: [],
    strokeColor: '#FF0000',
    strokeWeight: 3});

    var x = 0;
    DirectionService.route(request, function(result, status) {
        x = 1;
        if (status == google.maps.DirectionsStatus.OK)
        {
            var legs = result.routes[0].legs;       
            for ( i = 0; i < legs.length; i++) {
                var steps = legs[i].steps;
                for ( j = 0; j < steps.length; j++) {
                    var nextSegment = steps[j].path;
                    for ( k = 0; k < nextSegment.length; k++) {
                        polyline.getPath().push(nextSegment[k]);]
                    }
                }
            }
        console.log(polyline.getPath().getArray().length); // not zero
        console.log(x) // x = 1;
    }
});

map = new google.maps.Map(document.getElementById("googleMap"),mapProp);
console.log(polyline.getPath().getArray().length); // the array length is 0
console.log(x) // x remains ZERO!!

Answer 1

console.log（x）（最后）在执行回调函数之前触发。记住并发性。

回调中的变量不能改变

1 个答案: