Convert 2 bundle analyzer outputs to a markdown table

bundles-to-markdown.js

#!/usr/bin/env node

const fs = require("fs").promises;
const path = require("path");

const filename = path.resolve(process.argv[2]);

// Match like "name-bundle.c660430462be77d62c18.js (2.02 MB)"
const regex = /(.+)\s\((.+)\)/;

async function getFileLines() {
  let contents;
  try {
    const buffer = await fs.readFile(filename);
    contents = buffer.toString();
  } catch (error) {
    console.error(error);
  }

  return contents.split("\n");
}

function getBundleComparison(lines) {
  const data = {};
  const sizes = new Map();

  let isBeforeBundle = true;

  for (line of lines) {
    if (line === "---") {
      isBeforeBundle = false;
      continue;
    }

    const match = regex.exec(line);

    if (!match) {
      continue;
    }

    const key = match[1];
    let filename = key;
    const size = match[2];
    const hasFilename = !!data[filename];

    // If the current filename isn't already tracked, there is a file with the
    // same size, and that pair hasn't been "used", use the existing filename with that size.
    if (!hasFilename && sizes.has(size) && sizes.get(size).length === 1) {
      [filename] = sizes.get(size);
    } else if (!hasFilename) {
      // Otherwise, if the filename isn't tracked yet, create the initial data for it.
      data[filename] = {
        before: "",
        after: "",
      };
    }

    // Update the sizes map with this line item.
    sizes.set(size, [...(sizes.get(size) || []), key]);

    // Update the pairs object.
    data[filename][isBeforeBundle ? "before" : "after"] = size;
  }

  return data;
}

function getMarkdown(comparison) {
  const header = "| filename | before | after |\n|----|---|----|\n";
  const rows = Object.entries(comparison).map(
    ([key, value]) =>
      `| ${key.replace(/~/g, "\\~")} | ${value.before} | ${value.after} |`
  );
  return `${header}${rows.join("\n")}`;
}

async function run() {
  const lines = await getFileLines();
  const data = getBundleComparison(lines);
  const markdown = getMarkdown(data);
  console.log(markdown);
}

run();

example-bundles.txt

All (5.8 MB)
static/chunks/pages/_app-080c77e111409ccf344c.js (3.55 MB)
static/chunks/e881dd8a.aaabad384ef2dd6439e9.js (939.47 KB)
static/chunks/48d18726.2f59de87fa2aedcb1498.js (388.16 KB)
static/chunks/a48ca981.bdc7c53768d4798b9d15.js (229.56 KB)
static/chunks/895b5e10.4b5760a4d28bdeb6b2b2.js (136.05 KB)
static/chunks/framework.3519294afa6a9ab53973.js (126.21 KB)
static/chunks/styles.68029285599d666b2795.js (102.92 KB)
static/chunks/polyfills-dca1b5a048b3a0e31e64.js (90.02 KB)
static/chunks/2ca616f1.cd0818a071e817fd846e.js (76.72 KB)
static/chunks/0f1ac474.621d2ab38f9a717aa56b.js (70.96 KB)
static/chunks/8313d723.8c0b0bb88b23a35736ed.js (55.09 KB)
static/chunks/4f149b58.17486bb937b4246f3e79.js (40.53 KB)
static/chunks/d1edcd509e188af8a3b11bf83ac465d1fbfeb83c.5430ff9842d7e64d56e3.js (23.55 KB)
static/chunks/main-6c6004c60ac0c2336b18.js (14.56 KB)
static/chunks/pages/_error-0131dd55816b8301f155.js (7.73 KB)
static/chunks/webpack-7bd1a373f3b01d510bde.js (2.37 KB)
static/chunks/pages/[...index]-56225315d3fa5ef4a3a3.js (432 B)
static/chunks/18.0a7cc9f0537c413437d6.js (427 B)
static/chunks/pages/index-5eab8ab0e603d341c697.js (422 B)

---

All (4.24 MB)
static/chunks/pages/_app-612c700ab77ed90ec7e1.js (2.06 MB)
static/chunks/e881dd8a.1155fcfe5c80df89a716.js (939.47 KB)
static/chunks/48d18726.664a8c4aeed362960d23.js (388.16 KB)
static/chunks/a48ca981.975808537899b456f308.js (229.56 KB)
static/chunks/895b5e10.92a4d6d86157057f626b.js (136.05 KB)
static/chunks/framework.3519294afa6a9ab53973.js (126.21 KB)
static/chunks/styles.7451907771067f2e0c7b.js (102.92 KB)
static/chunks/polyfills-c8cc3525c437fef2c42f.js (90.02 KB)
static/chunks/0f1ac474.71ee40e286ebcca351c0.js (70.96 KB)
static/chunks/8313d723.b781d686a875b4b6e5b3.js (55.09 KB)
static/chunks/4f149b58.47f6f9cb8f554b494ae7.js (40.53 KB)
static/chunks/d1edcd509e188af8a3b11bf83ac465d1fbfeb83c.5430ff9842d7e64d56e3.js (23.55 KB)
static/chunks/main-291ce000fe6e5cb7c8b4.js (14.56 KB)
static/chunks/pages/_error-92d2a152b77934e80423.js (7.73 KB)
static/chunks/webpack-898126f19adf8cd83d35.js (2.37 KB)
static/chunks/pages/[...index]-b6ab3b2770240c203545.js (432 B)
static/chunks/17.5e77338df8bbdf71a40d.js (427 B)
static/chunks/pages/index-2108d97d88461fe75fe6.js (422 B)