Node.js read and write post status to a JSON file

— 5 minute read

A while ago, I started building my RSS reader to auto-publish to certain platforms, but we never finished it 👀.

Today we will be looking into looping over the articles we get via the RSS reader and keeping track of which ones are posted to the socials.

Pre-condition: You need to know how to set up a basic node app 👈

What you'll learn from this article

  • Read data from a JSON file in Node.js
  • Write data to a JSON file in Node.js
  • Reading RSS data
  • Keeping track of run changes

Setting up our JSON file

Our JSON file is going to be quite easy in structure and will look as follows:

{
  "https://daily-dev-tips.com/posts/rss-reader-in-node-js": {
    "published": true
  },
  "https://daily-dev-tips.com/posts/top-10-chrome-extensions-for-developers-👀": {
    "published": true
  }
}

We basically only need to know if an object is already on this list.

Looping through our RSS feed

First, we need to add the rss-parser package.

npm i rss-parser

Then we can loop through our articles using the sitemap we have.

let Parser = require('rss-parser');
let parser = new Parser();

(async () => {
  let feed = await parser.parseURL('https://daily-dev-tips.com/sitemap.xml');

  feed.items.forEach((item) => {
    console.log(item.id);
  });
})();

Now we need to make sure we read our JSON file and see if we have already published this article.

First, let's define the file-system.

const fs = require('fs');

Then we can read out actual JSON file

let rawdata = fs.readFileSync('site.json');
let siteData = JSON.parse(rawdata);

This will at first we an empty object {}.

In our loop we need to check if we already published this item. If yes => Don't do anything If no => Do magic and then add to JSON file.‌

feed.items.forEach((item) => {
  let url = item.id;
  if (!siteData.url) {
    // Do magic posting stuff
    siteData[url] = {
      published: true,
    };
  }
});

Once the loop is done, we can save our JSON to the actual file.

fs.writeFileSync('site.json', JSON.stringify(siteData));

Our JSON file will then look something like this.

{
  "https://daily-dev-tips.com/posts/vanilla-javascript-canvas-images-to-black-and-white/": {
    "published": true
  },
  "https://daily-dev-tips.com/posts/vanilla-javascript-images-in-canvas/": {
    "published": true
  },
  "https://daily-dev-tips.com/posts/vanilla-javascript-colouring-our-canvas-elements-🌈/": {
    "published": true
  }
}

Awesome, we now parsed our RSS feed, read our JSON file, and wrote data to it if not already in there!

You can find this project on GitHub.

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