Question

I’m trying to filter out addresses on a Google map based on driving/walking duration.
However, it seems like I’m missing something really basic in how this Javascript snippet runs:

//addresses that I'd like to compare to a point of origin
var addresses = ['address_1','address_2','address_3','address_4','address_5'];
//point of interest/origin
var origin = 'origin_address';

for (i=0;i<addresses.length;i++){
  var directionsService = new google.maps.DirectionsService();
  var directionsDisplay = new google.maps.DirectionsRenderer();
  directionsDisplay.setMap(map);

  var request = {
    origin: origin, 
    destination: addresses[i],
    travelMode: google.maps.DirectionsTravelMode.DRIVING
    };

  directionsService.route(request, function(response, status) {
    if (status == google.maps.DirectionsStatus.OK) {
      //====> Why can't I access results[i] here? I get "undefined" for the following
      alert(addresses[i]);

      // I get 3 identical values, then a unique fourth value
      alert(response.routes[0].legs[0].duration.value);

      //if the duration is below a certain value, I'd like to show a marker.
      //however, I can't do that, since I can't access addresses[i]
      if(response.routes[0].legs[0].duration.value < 1200){
        //Geocode address & show marker
      }
    }
  });
}

Any idea why:
1) I can’t access the variable “addresses” from inside: directionsService.route(request, function(response, status) {
//…..HERE…..
});

2) Is this the right way to compare durations for different routes, or am I doing something seriously inefficient?

Thanks a lot!

Answer 1

That function is a callback function. Its scope is different fro. what you might think it is. In that function, i doesn’t exist.

My phone is really bad for SO, but Your response variable will have the address you are looking for from you request variable.

EDIT

You can try closures:

directionsService.route(request, (function (address) {
    return function(response, status) {
    if (status == google.maps.DirectionsStatus.OK) {
      //====> Why can't I access results[i] here? I get "undefined" for the following
      alert(address);

      // I get 3 identical values, then a unique fourth value
      alert(response.routes[0].legs[0].duration.value);

      //if the duration is below a certain value, I'd like to show a marker.
      //however, I can't do that, since I can't access addresses[i]
      if(response.routes[0].legs[0].duration.value < 1200){
        //Geocode address & show marker
      }
    })(addresses[i])
  });