Extract assets from Webpack compilation

getAssetsByChunkNames.js

/**
 * @param {Compilation} compilation Webpack compilation
 * @returns {{
 *   byChunkName: {chunkName: Array<{name: string, source: string}>},
 *   extra: Array<{name: string, source: string}> 
 * }}
 */
var getAssets = function (compilation) {
  var EXTRA_ASSETS_CHUNK_NAME = '__extra_assets__';
  var stats = compilation.getStats().toJson();
  var compiledAssets = compilation.assets;
  var chunks = {};

  stats.assets.forEach(function (assetInfo) {
    assetInfo.chunkNames.forEach(function (chunkName) {
      if (chunkName in chunks == false)
        chunks[chunkName] = [];

      chunks[chunkName].push({
        name: assetInfo.name
      })
    });
  });

  // Assets with no chunks
  var extraAssets = stats.assets.filter(function(assetInfo) {
    return assetInfo.chunks.length == 0
  }).map(function(assetInfo) {
    return {
      name: assetInfo.name
    }
  });
  
  chunks[EXTRA_ASSETS_CHUNK_NAME] = extraAssets;

  // Sources
  for (var chunkName in chunks) {
    var assets = chunks[chunkName];
    
    assets.forEach(function(asset) {
      if (asset.name in compiledAssets)
        asset.source = compiledAssets[asset.name].source();
    })
  }
  
  delete chunks[EXTRA_ASSETS_CHUNK_NAME];
  
  return {
    byChunkName: chunks,
    extra: extraAssets
  };
};