Resolve aliases given email in appscripts.

ResolveAlias.js

function resolveAlias_(email) {
  var resp, ret;
  try {
    resp = AdminDirectory.Users.Aliases.list(email);
  } catch(e) {
    if (e.message === 'Resource Not Found: userKey') {
      return null;
    }
    return null;
  }
  if (resp.aliases) {
    var primaries;
    primaries = resp.aliases.reduce(
      function (acc, aliasRecord) {
        if (acc.indexOf(aliasRecord.primaryEmail) === -1) acc.push(aliasRecord.primaryEmail);
        return acc;
      }, []
    );
    if (primaries.length > 1) throw Error("More than one primary email!");
    ret = primaries[0];
  } else {
    ret = email;
  }
  return ret;
}