Synchronous/sequential REST calls in loop - node.js

Question

I'm trying to call a REST API in a "for" loop, however, the results aren't what I'm expecting.
I've attempted to wrap everything in a promise, but the order of operations is still off, executing it asynchronously rather than synchronously.
var https = require('https');
var zlib = require("zlib");
var axios = require('axios');
const cheerio = require('cheerio');
var page = 1;
var hasMore = "true";
function delay() {
return new Promise(resolve => setTimeout(resolve, 300));
}
async function getLocation(page) {
// notice that we can await a function
// that returns a promise
await delay();
var apiUrl = 'https://my.api.com/search/advanced?page=' + page +
'&pagesize=5';
https.get(apiUrl, function(response) {
console.log("headers: ", response.headers);
console.log(response.statusCode)
if (response.statusCode == 200) {
var gunzip = zlib.createGunzip();
var jsonString = '';
response.pipe(gunzip);
gunzip.on('data', function(chunk) {
jsonString += chunk;
});
gunzip.on('end', function() {
obj = JSON.parse(jsonString);
var url = obj.items[0].owner.link;
axios(url)
.then(response => {
const html = response.data;
const $ = cheerio.load(html);
//OUTPUT LOCATION
console.log($('h3.location').text().trim());
})
.catch(console.error);
});
gunzip.on('error', function(e) {
console.log(e);
});
} else {
console.log("Error");
}
});
}
async function startGetLocation() {
var page = 1;
var hasMore = "true";
do {
//OUTPUT PAGE NUMBER
console.log(page.toString());
await getLocation(page);
page = page + 1;
} while (page < 3);
}
startGetLocation();
Based on the sample code, I would have expected the below to output:
1
New York
2
However, it's outputting:
1
2
New York

Answer 1

The problem is that the callback function that you passed to the https.get() function gets executed asynchronously and that the getLocation function does not wait until this part resolves.
So you could simply wrap the https.get() call and the unzipping part in a promise, wait for it to resolve and then do the axios-part.
async function getLocation(page) {
await delay();
var apiUrl = 'https://my.api.com/search/advanced?page=' + page +
'&pagesize=5';
const fetchAndUnzipPromise = new Promise((resolve, reject) => {
https.get(apiUrl, function (response) {
console.log("headers: ", response.headers);
console.log(response.statusCode)
if (response.statusCode == 200) {
var gunzip = zlib.createGunzip();
var jsonString = '';
response.pipe(gunzip);
gunzip.on('data', function (chunk) {
jsonString += chunk;
});
gunzip.on('end', function () {
obj = JSON.parse(jsonString);
var url = obj.items[0].owner.link;
resolve(url);
});
gunzip.on('error', function (e) {
reject(e);
});
} else {
reject(new Error("Statuscode not as exepcted"));
}
});
});
return fetchAndUnzipPromise.then(url => {
return axios(url)
.then(response => {
const html = response.data;
const $ = cheerio.load(html);
//OUTPUT LOCATION
console.log($('h3.location').text().trim());
})
.catch(console.error);
})
}