Google Elevation API - splitting multiple elevation requests - google-maps

Question

I'm trying to split a big request for elevation into multiple requests to avoid the 1sec/request and 512 coords limit in each request.
The problem I face is that the reply of my requests are not always received in the good order. Is using setInterval reliable enough?
Here is an example of response received in the wrong order that cause a problem (before using setInterval):
https://www.dropbox.com/s/x00jdnprj6w7lga/correctMap.png?dl=0
Here is my latest code:
function getCourseElevationData() {
var path = bikePathCoordinates; //Bunch of lat,long coords
// numberRequestToDo = Math.ceil(path.length/512); //TODO: split request in multiple 512 pack (google quotas)
numberRequestToDo = 2; //Temporary for testing
currentRequestNumber = -1; //will be at 0 on first call to get512Elevation
arrayOfRequest = [];
//1
var ptrStart= 0;
var pathSliced = path.slice(ptrStart, ptrStart+512);
arrayOfRequest.push(pathSliced);
//2
ptrStart += 512;
pathSliced = path.slice(ptrStart, ptrStart+512);
arrayOfRequest.push(pathSliced);
timerElevation = setInterval(request512Elevation, 1000); //1sec
}
//---------------------------------------------------------
function request512Elevation() {
alert("request512Elevation");
// Still has request to be done
if (currentRequestNumber+1 < numberRequestToDo) {
if (!lastRequestElevationFailed) {
currentRequestNumber++;
}
get512Elevation(arrayOfRequest[currentRequestNumber], currentRequestNumber);
}
// All request completed!
else {
clearInterval(timerElevation);
}
}
//------------------------------------------------------------------------------------------------
function get512Elevation(pathSliced, requestNumber) {
alert("get512PointsElevation" + requestNumber);
var locationElevationRequest = {
'locations': pathSliced
}
elevator.getElevationForLocations(locationElevationRequest, function (results, status) {
alert("ResponseReceived for request:" + requestNumber + ", status" + status + " result length:" + results.length);
if (status != google.maps.ElevationStatus.OK) {
lastRequestElevationFailed = true;
return;
}
lastRequestElevationFailed = false;
var elevations = results;
// Extract the elevation samples from the returned results
for (var i = 0; i < results.length; i++) {
elevationPath.push(elevations[i].location);
}
for (var i = 0; i < results.length; i++) {
dataElevation.addRow(['', elevations[i].elevation]);
}
//last reply received? if yes, we can display the elevation graph
if (currentRequestNumber+1 == numberRequestToDo) {
chart.draw(dataElevation, chartOptions);
}
//TODO: how to make sure response are received in correct order (1,2,3)? setInterval reliable enough?
});
}