Question

I need to add a 1 second delay between each plot of my markers. I came up with the following code but cannot make it work. Any idea ?

var latlng = new google.maps.LatLng(43,2.34);
var myOptions = {
  zoom: 7,
  center: latlng,
  mapTypeId: google.maps.MapTypeId.ROADMAP
};
var map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);

for ( var i=0, len=json.length; i<len; i++ ){
  obj = json[i];

  // Get lat / long and put them on the map
  var lat = obj.latitude;
  var long = obj.longitude;

  display_marker(map, lat, long);
}

display_marker = function(map, lat, long){
  setTimeout(function(){}, 1000);
  var marker = new google.maps.Marker({
    map: map,
    position: new google.maps.LatLng(lat,long),
    title: "Latitude: " +  lat + "\nLongitude: " + long,
  });
}

Answer 1

there a 2 things going wrong right here.

the first one is, that you use the setTimeout with an empty function. your code needs to be inside that function:

display_marker = function(map, lat, long){
  setTimeout(function() {
    var marker = new google.maps.Marker({
      map: map,
      position: new google.maps.LatLng(lat,long),
      title: "Latitude: " +  lat + "\nLongitude: " + long,
    });
  }, 1000);
}

the second on is, that your loop triggers the display_marker one after the other, so if you fix problem 1, even then you all your markers will be generated after ~1000ms

an easy way to fix this, is to pass the current value if your increment-var to your display marker, and multiply it for your setTimeout:

var obj, lat, long;
for ( var i=0, len=json.length; i<len; i++ ){
  obj = json[i];

  // Get lat / long and put them on the map
  lat = obj.latitude;
  long = obj.longitude;

  display_marker(map, lat, long, i);
}

display_marker = function(map, lat, long, increment){
  setTimeout(function() {
    var marker = new google.maps.Marker({
      map: map,
      position: new google.maps.LatLng(lat,long),
      title: "Latitude: " +  lat + "\nLongitude: " + long,
    });
  }, increment * 1000);
}

hint: see what i did with the variable declarations. you were redeclaring the variables inside your loop

hint2: my code is untested, but it should give you the right idea how to solve your problem