addUrls.js

const fs = require('fs');
const request = require('request');

const properties = 'css/properties.json';
const urlTemplate = 'https://developer.mozilla.org/docs/Web/CSS/{{replaceme}}';
const urlRegex = new RegExp('{{replaceme}}');

function main() {
  const obj = parseJSONFile(properties);
  let lookups = {};
  let pendingRequests = [];

  for (let key in obj) {
    let url = makeMDNURL(key);

    pendingRequests.push(head(url).then((result) => {
      lookups[key] = {
        'name': key,
        'url': url,
        'statusCode': result.statusCode,
        'newurl': result.request.uri.href
      };
    }));
  }

  Promise.all(pendingRequests).then(() => {
    for (let item in lookups) {
      console.error(`Checking ${lookups[item].name}`);
      let statusCode = lookups[item].statusCode;

      if (statusCode == 404 || statusCode == 429) {
        console.error(`ERROR: ${lookups[item].url} -- URL was not found [${statusCode}]`);
      }
      else {
        if (isRedirected(lookups[item].url, lookups[item].newurl)) {
          console.error(`WARNING: ${lookups[item].url} -- URL was redirected`);
        }
        console.error(`Adding ${lookups[item].url}`);
        obj[item]['mdn_url'] = lookups[item].url;
      }
    }
    console.log(JSON.stringify(obj, null, 2));
  });
}

function isRedirected(url, newurl) {
  let delocalized = newurl.replace('en-us/');
  return delocalized == url;
}

function parseJSONFile(filepath) {
  return JSON.parse(fs.readFileSync(filepath, 'utf-8'));
}

function makeMDNURL(name) {
  return urlTemplate.replace(urlRegex, name);
}

function head(url) {
  return new Promise((resolve, reject) => {
    request.head(url)
      .on('response', (response) => {
        resolve(response);
      })
      .on('error', (err) => { reject(err); });
  });
}


main();