JavaScript Async Loop不返回结果

Question

尝试在JavaScript中执行函数时遇到了一些逻辑问题。基本上我有一个pointArr来存储沿路线的坐标。然后我得到一个moveNext（），它接收沿着路线的每个坐标并绘制到地图上。然后在moveNext（）内部，我得到另一个数组，它是busList。如果沿着路线的坐标与busList的坐标匹配，那么我将totalBusStopLeft减去一。这是我调用moveNext（）的代码：

 getAllBusLoc(function(busList) {
            //At first I set the totalBusLeft by the length of busList which is 13 in this case
            var totalBusLoc = busList.length;
            document.getElementById("busStopLeft").innerHTML = totalBusLoc;
            //Then I set the value to busList for the minus calculation
            busLeft = totalBusLoc;
            timeout = 1500;
            pointArr.forEach(function(coord,index){
                setTimeout(function(){
                    moveNext(coord.x, coord.y, index, busList, busLeft);
                }, timeout * index);
            });
        });

function moveNext(coordx, coordy, k, busList, busLeft){
document.getElementById("busStopLeft").innerHTML = busLeft;
//pointToCompare is the coordinates in the route but not the coordinates of busList
var pointToCompare = coordx + "," + coordy;

//If the coordinates in route matches the coordinate in busList, I minus busLeft by one
if(busList.indexOf(pointToCompare) > -1){
     parseFloat(busLeft--);
}

//Code to Add marker

}

但是，使用此代码，我的Html组件busStopLeft继续显示13，即totalBusLoc，但不是busLeft。有任何想法吗？

提前致谢。

修改

    totalBusLoc = busList.length;
            document.getElementById("busStopLeft").innerHTML = totalBusLoc;
            timeout = 1500;
            pointArr.forEach(function(coord,index){
                setTimeout(function(busLeft){
                    moveNext(coord.x, coord.y, index, busList, totalBusLoc);
                }, timeout * index);
            });
        });


function moveNext(coordx, coordy, k, busList, totalBusLoc, callback){
var pointToCompare = coordx + "," + coordy;
if(busList.indexOf(pointToCompare) > -1){
     parseFloat(totalBusLoc--);
     document.getElementById("busStopLeft").innerHTML = totalBusLoc;
     callback(totalBusLoc);
}
}