react-native/packager/src/node-haste/DependencyGraph/DependencyGraphHelpers.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.
 *
 * @flow
 */

'use strict';

const path = require('path');

const NODE_MODULES = path.sep + 'node_modules' + path.sep;

class DependencyGraphHelpers {

  _providesModuleNodeModules: Array<string>;
  _assetExts: Array<string>;

  constructor({providesModuleNodeModules, assetExts}: {
    providesModuleNodeModules: Array<string>,
    assetExts: Array<string>,
  }) {
    this._providesModuleNodeModules = providesModuleNodeModules;
    this._assetExts = assetExts;
  }

  isNodeModulesDir(file: string) {
    const index = file.lastIndexOf(NODE_MODULES);
    if (index === -1) {
      return false;
    }

    const parts = file.substr(index + 14).split(path.sep);
    const dirs = this._providesModuleNodeModules;
    for (let i = 0; i < dirs.length; i++) {
      if (parts.indexOf(dirs[i]) > -1) {
        return false;
      }
    }

    return true;
  }

  isAssetFile(file: string) {
    return this._assetExts.indexOf(this.extname(file)) !== -1;
  }

  extname(name: string) {
    return path.extname(name).substr(1);
  }
}

module.exports = DependencyGraphHelpers;