Add some stats to the 'yarn build' command

resources/build.js

@@ -2,6 +2,7 @@
 
 'use strict';
 
+const fs = require('fs');
 const path = require('path');
 const assert = require('assert');
 const babel = require('@babel/core');
@@ -35,6 +36,53 @@ if (require.main === module) {
   );
 
   writeFile('./dist/package.json', JSON.stringify(packageJSON, null, 2));
+  showStats();
+}
+
+function showStats() {
+  const fileTypes = {};
+  let totalSize = 0;
+
+  for (const filepath of readdirRecursive('./dist')) {
+    const name = filepath.split(path.sep).pop();
+    let [base, ...ext] = name.split('.');
+    ext = ext.join('.');
+
+    const filetype = ext ? '*.' + ext : base;
+    fileTypes[filetype] = fileTypes[filetype] || { filepaths: [], size: 0 };
+
+    const { size } = fs.lstatSync(path.join('./dist', filepath));
+    totalSize += size;
+    fileTypes[filetype].size += size;
+    fileTypes[filetype].filepaths.push(filepath);
+  }
+
+  let stats = [];
+  for (const [filetype, typeStats] of Object.entries(fileTypes)) {
+    const numFiles = typeStats.filepaths.length;
+
+    if (numFiles > 1) {
+      stats.push([filetype + ' x' + numFiles, typeStats.size]);
+    } else {
+      stats.push([typeStats.filepaths[0], typeStats.size]);
+    }
+  }
+  stats.sort((a, b) => b[1] - a[1]);
+  stats = stats.map(([type, size]) => [type, (size / 1024).toFixed(2) + ' KB']);
+
+  const typeMaxLength = Math.max(...stats.map(x => x[0].length));
+  const sizeMaxLength = Math.max(...stats.map(x => x[1].length));
+  for (const [type, size] of stats) {
+    console.log(
+      type.padStart(typeMaxLength) + ' | ' + size.padStart(sizeMaxLength),
+    );
+  }
+
+  console.log('-'.repeat(typeMaxLength + 3 + sizeMaxLength));
+  const totalMB = (totalSize / 1024 / 1024).toFixed(2) + ' MB';
+  console.log(
+    'Total'.padStart(typeMaxLength) + ' | ' + totalMB.padStart(sizeMaxLength),
+  );
 }
 
 function babelBuild(srcPath, envName) {