create-react-app/packages/react-dev-utils/FileSizeReporter.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

'use strict';

var fs = require('fs');
var path = require('path');
var chalk = require('chalk');
var filesize = require('filesize');
var recursive = require('recursive-readdir');
var stripAnsi = require('strip-ansi');
var gzipSize = require('gzip-size').sync;

// Prints a detailed summary of build files.
function printFileSizesAfterBuild(webpackStats, previousSizeMap) {
  var root = previousSizeMap.root;
  var sizes = previousSizeMap.sizes;
  var assets = webpackStats
    .toJson()
    .assets.filter(asset => /\.(js|css)$/.test(asset.name))
    .map(asset => {
      var fileContents = fs.readFileSync(path.join(root, asset.name));
      var size = gzipSize(fileContents);
      var previousSize = sizes[removeFileNameHash(root, asset.name)];
      var difference = getDifferenceLabel(size, previousSize);
      return {
        folder: path.join('build', path.dirname(asset.name)),
        name: path.basename(asset.name),
        size: size,
        sizeLabel: filesize(size) + (difference ? ' (' + difference + ')' : '')
      };
    });
  assets.sort((a, b) => b.size - a.size);
  var longestSizeLabelLength = Math.max.apply(
    null,
    assets.map(a => stripAnsi(a.sizeLabel).length)
  );
  assets.forEach(asset => {
    var sizeLabel = asset.sizeLabel;
    var sizeLength = stripAnsi(sizeLabel).length;
    if (sizeLength < longestSizeLabelLength) {
      var rightPadding = ' '.repeat(longestSizeLabelLength - sizeLength);
      sizeLabel += rightPadding;
    }
    console.log(
      '  ' +
        sizeLabel +
        '  ' +
        chalk.dim(asset.folder + path.sep) +
        chalk.cyan(asset.name)
    );
  });
}

function removeFileNameHash(buildFolder, fileName) {
  return fileName
    .replace(buildFolder, '')
    .replace(/\/?(.*)(\.\w+)(\.js|\.css)/, (match, p1, p2, p3) => p1 + p3);
}

// Input: 1024, 2048
// Output: "(+1 KB)"
function getDifferenceLabel(currentSize, previousSize) {
  var FIFTY_KILOBYTES = 1024 * 50;
  var difference = currentSize - previousSize;
  var fileSize = !Number.isNaN(difference) ? filesize(difference) : 0;
  if (difference >= FIFTY_KILOBYTES) {
    return chalk.red('+' + fileSize);
  } else if (difference < FIFTY_KILOBYTES && difference > 0) {
    return chalk.yellow('+' + fileSize);
  } else if (difference < 0) {
    return chalk.green(fileSize);
  } else {
    return '';
  }
}

function measureFileSizesBeforeBuild(buildFolder) {
  return new Promise(resolve => {
    recursive(buildFolder, (err, fileNames) => {
      var sizes;
      if (!err && fileNames) {
        sizes = fileNames
          .filter(fileName => /\.(js|css)$/.test(fileName))
          .reduce((memo, fileName) => {
            var contents = fs.readFileSync(fileName);
            var key = removeFileNameHash(buildFolder, fileName);
            memo[key] = gzipSize(contents);
            return memo;
          }, {});
      }
      resolve({
        root: buildFolder,
        sizes: sizes || {},
      });
    });
  });
}

module.exports = {
  measureFileSizesBeforeBuild: measureFileSizesBeforeBuild,
  printFileSizesAfterBuild: printFileSizesAfterBuild,
};