I'm using request to make HTTP requests inside a loop of variable size. (I will be reading words from a file, right now I just have an array). I'm adding onto an object (response) with each loop, and want to return the object only after the last request has been completed. I've been playing around with promises but I'm not sure how to chain them since it is a variable number of requests.
const request = require('request');
// eventually this array will be populated by reading a file
var words = ["hello", "there"];
var response = {};
// Loop thruogh input string
for (var i = 0; i < words.length; i += 1) {
// get next word
var curWord = words[i];
// if the current word is not already in the response
if (!(curWord in response)) {
// request info from dictionary
var options = {
url: 'https://api.dictionaryapi.dev/api/v2/entries/en/' + curWord,
json: true
}
request(options, (err, res, body) => {
if (err) { return console.log(err); }
// find part of speech
var partOfSpeech;
try {
partOfSpeech = body[0].meanings[0].partOfSpeech
} catch (err) {
partOfSpeech = "undefined";
}
// add to response
response[curWord] = partOfSpeech;
});
}
}
// do this part only after last request has been completed
console.log(response);
Basically you need to count the responses knowing that when counter reaches zero you are done with them all.
EDIT: make sure you are referring the same curWord parameter in the response to match the request. This is done using the IIFE there.
I have setup an example for you
const request = function fake_request(options, callback) {
setTimeout(function() {
callback(null, options.url.slice(options.url.lastIndexOf('/')))
}, Math.random() * 1000)
};
var words = ["hello", "there", "angela"];
var count = words.length;
var response = {}
for (var i = 0; i < words.length; i += 1) {
var curWord = words[i];
if (!(curWord in response)) {
var options = {
url: 'https://api.dictionaryapi.dev/api/v2/entries/en/' + curWord,
json: true
};
(function(curWord) {
request(options, (err, res, body) => {
count--
console.log(count)
partOfSpeech = res;
response[curWord] = partOfSpeech;
if (count == 0) {
// do this part only after last request has been completed
console.log(response);
}
});
})(curWord);
}
}