code: function findDir(dirList, ifCb, elseCb) {
    async.detect(dirList, dirExists, function (dir) {
      if (dir) {
        ifCb(dir);
      } else {
        elseCb();
      }
    });
  }
docs: /*
  Find one of a list of directories.
  @param {Array} dirList Possible directories to find.
  @param {function} ifCb If one is found, do this.
  @param {function} elseCb If one is not found, do this.