Synchronous http request in node js? - node.js

Question

I'm looking for a simple way to perform synchronous http-requests in node.js, but it's still getting async responses ...
I've realised that node.js is recommended to async jobs, but in my case,
I need the synchronous response to call other functions that use this data, if it's null/undefined, I can't proceed with the flow...
What's the better way to do that?
Here's my code:
function callCellId(data) {
console.log("Data: " + data);
var towers = [],
rscp = [];
var request = require('sync-request');
for (var x = 0; x < data.length; x++) {
console.log("Request data: \n");
rscp[x] = data[x].rscp;
var res = request('POST', 'http://opencellid.org/cell/get?key=xxxxx&mcc=' + data[x].mcc + '&mnc=' + data[x].mnc + '&lac=' + data[x].LAC + '&cellid=' + data[x].cellID + '&format=json');
console.log("loop " + x);
data = res.getBody().toString();
console.log("rsp: " + data);
towers[x] = {
'latitude': data.lat,
'longitude': data.lon,
'rscp': rscp[x],
'signal': data.averageSignalStrength
};
}
console.log("Content for triangulation" + JSON.stringify(towers));
return towers;
}

Answer 1

Using async in a loop cloud be tricky.
I solved this without external libraries using generators:
LoopOperation: function() {
//define generator with the main loop
var loopIterator = function*() {
for (var index = 0; index < 10; index++) {
var result = yield asyncOperation( (res) => loopIterator.next(res)); //do something asyc and execute () => loopIterator.next() when done as callback
console.log(result);
}
}();
loopIterator.next(); //start loop
}

Answer 2

Since the nodejs nature is async, every time we need some sync call (like this nested request stack), we're able to use promises
"A Promise is an object representing the eventual completion or failure of an asynchronous operation"
reference
I.E:
const request = require('request-promise');
function callCellId(data) {
let towers = [];
let options = {
url: 'http://opencellid.org/cell/get',
method: 'POST',
json: true
};
data.forEach(location => {
options.body = {
key: 'YOUR_PRIVATE_KEY',
mcc: location.mcc,
mnc: location.mnc,
lac: location.lac,
cellId: location.cellID
}
request(options).then(cellInfo => {
towers.push({
latitude: cellInfo.lat,
longitude: cellInfo.lon,
rscp: location.rscp,
signal: cellInfo.averageSignalStrength
});
}).catch(err => {
console.log('Could not get cellId Info for',location);
console.log(err);
});
});
return towers;
}