CODEWITHSUNDEEP
javascriptjsonnode.js
dace
dace

Reputation: 6363

Getting null when looping through JSON and writing to a file in node

I'm looping through 2 JSON objects. One contains an array of country objects and the other is an array of airport objects. I'd like to loop through and return a model that combines information from both if that airport's country matches the current country:

const fs = require('fs');
const allData = require('./airports.json');
const countryCodes = require('./codes.json');

const newData = countryCodes.map(country => {
    allData.map(airport => {
        if (country.name === airport.country) {
            // console.logging here shows me that my equality check is working...
            return {
                "airport": `${airport.code} - ${airport.name}`,
                "countryName": `${airport.country}`,
                "countryCode": `${country["alpha-2"]}`
            }
        }
    })
})

fs.writeFile("./newAirlines.json", JSON.stringify(newData, null, 2), function(err) {
    if (err) {
        console.log(err);
    }
});

However, when I open the newAirlines.json file it writes to, I just get an array of null, null, null... Wondering if this has something to do with the asynchronously trying to write to a file before it has a chance to finish looping through (?), but am not sure.

Any and all help is appreciate. Thanks!

Upvotes: 0

Views: 46

Answers (1)

morecchia808
morecchia808

Reputation: 456

Your newData variable is not returning anything. You should populate an array an from inside the second iteration instead of calling map again on the airport array. For example:

    const newAirlines = []
    const newData = countryCodes.forEach(country => {    
      allData.forEach(airport => {
        if (country.name === airport.country) {
          newAirlines.push({
            "airport": `${airport.code} - ${airport.name}`,
            "countryName": `${airport.country}`,
            "countryCode": `${country["alpha-2"]}`
          })
        }
      })
     })

    fs.writeFile("./newAirlines.json", JSON.stringify(newAirlines, null, 2), function(err) {
      if (err) {
        console.log(err);
      }
    })

Upvotes: 1

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