Multi tool use

Passing parameters to imported function in Node.js

I feel like this shouldn't be hard, but I'm new to Node.js (and also new to many aspects of JavaScript). I'm creating an Express application to return arrays of bike locations that are fetched from multiple APIs; each API requires the longitude and latitude as inputs. So I've broken each API call into a 'module' and I'm using the npm library 'async' to make each call in parallel, and using 'axios' to make the API requests. I can get it to work just fine without breaking it up into modules, but once I separate each API call into its own file, I can't figure out how to pass lat and lng into it.

Here is my index.js

import async from 'async';
import {mobike} from './mobike.js';
import {spin} from './spin.js';

async.parallel([
mobike, //How or where can I pass these parameters?
spin
],
function(err, results) {
console.log(results);
});


and here is my mobike.js module, for example (I'll omit spin.js for brevity)

import axios from 'axios';

export var mobike = function (lat, lng, callback){
axios.get('https://mwx.mobike.com/mobike-api/rent/nearbyBikesInfo.do', {
params: {
latitude: lat, //35.2286324
longitude: lng //-80.8427562
},
headers: {
'content-type': 'application/x-www-form-urlencoded',
'user-agent': 'Mozilla/5.0'
}
}).then( response => {
callback(null, response.data.object)
}).catch(error => {
callback(error, null)
})
}


When I try and pass arguments through mobike (like mobike(1234,1234)), it doesn't work. How can I pass the lat and lng arguments to the mobike.js file?

mobike(1234,1234)

async

promise

Promise.all

async.js

3 Answers
3

From a tutorial I found online, it looks like you need to wrap your mobike and spin functions inside other functions in order to bind in your data along with the callback function provided by the async module. Something like this:

mobike

spin

async

var lat = 35.2286324;
var lng = -80.8427562;

async.parallel([
function(callback) { mobike(lat, lng, callback); },
function(callback) { spin(lat, lng, callback); },
],
function(err, results) {
console.log(results);
});


For the parallel method each function only has a callback parameter.

The easiest way to achieve what you want is like this

async.parallel([
function (callback) {
var lng = 0.0
var lat = 0.0
mobike(lat, lng, callback), //This is where you pass in parameters
},
spin
],
function(err, results) {
console.log(results);
});


You can also use bind to pass parameters. Example:

const async = require('async')

const sleep = (ms = 0) => {
return new Promise(resolve => setTimeout(resolve, ms))
}

async.parallel([
mobike.bind(null, 1000), //How or where can I pass these parameters?
spin.bind(null, 500)
],
function(err, results) {
console.log(results);
})

async function mobike (ms) {
await sleep(ms) // pretend to wait for an api request
console.log('mobike waited for ' + ms + ' ms')
return ms
}

async function spin (ms) {
await sleep(ms) // pretend to wait for an api request
console.log('spin waited for ' + ms + ' ms')
return ms
}


Results:

spin waited for 500 ms
mobike waited for 1000 ms
[ 1000, 500 ]


By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.