Utility function to flatten an object with varied inner structure (Array, Object, string) into one flat array

gulp_flatten_paths.js

// Utility function to flatten an object with varied inner structure.
// Particularly useful in gulp when setting up a watch to listen for any file change.

// Arbitrary file path object
const paths = {
  module1: {
    js: [
      'src/app/**/*.js',
      'some_package/foo.js',
      'some_package/bar.js',
      'some_package/baz.js'
    ],
    html: [
      'src/app/index.html'
    ],
    css: [
      'src/app/styles.css'
    ]
  },
  module2: {
    js: [
      'src/app2/javascripts/**/*'
    ]
  },
  module3: {
    js: [
      'src/app/popup/**/*.js'
    ],
    html: 'src/app/popup/index.html'
  },
  webComponents: {
    html: ['src/web_components/**/*.html'],
    js:   ['src/web_components/foo/foo.js'],
    sass: ['src/web_components/**/*.scss']
  },
  manifest: 'src/config/manifest.json'
};

// This function will recursively traverse and flatten the paths object
const flattenPaths = (paths) => {
  const recursiveLookupHelper = (pathObj) =>{
    if (typeof(pathObj) === 'string') {
      fullPathList.push(pathObj);
    }
    else if (Array.isArray(pathObj)) {
      pathObj.map(innerPathObj => {
        recursiveLookupHelper(innerPathObj);
      });
    }
    else if (typeof(pathObj) === 'object') {
      Object.keys(pathObj).map(k => {
        recursiveLookupHelper(pathObj[k]);
      });
    }
  };

  let fullPathList = [];
  recursiveLookupHelper(paths);

  return fullPathList;
}


console.log(flattenPaths(paths));