Google+ Domain API with Apps Script

sample.js

var SCOPE_PLUS_ME = "https://www.googleapis.com/auth/plus.me";
var SCOPE_PLUS_PROFILES_READ = "https://www.googleapis.com/auth/plus.profiles.read";
var SCOPE_PLUS_CIRCLES_READ = "https://www.googleapis.com/auth/plus.circles.read";
var SCOPE_PLUS_CIRCLES_WRITE = "https://www.googleapis.com/auth/plus.circles.write";
var SCOPE_PLUS_STREAM_READ = "https://www.googleapis.com/auth/plus.stream.read";
var SCOPE_PLUS_STREAM_WRITE = "https://www.googleapis.com/auth/plus.stream.write";
var SCOPE_PLUS_MEDIA_UPLOAD = "https://www.googleapis.com/auth/plus.media.upload";

var SCOPES = [SCOPE_PLUS_ME,SCOPE_PLUS_STREAM_WRITE].join("+");
var USER_ID = "me";
var API_KEY = ScriptProperties.getProperty("apiKey");
var apiName = "GPlusDomainApp6";

function test() {
  
  var oauthConfig = UrlFetchApp.addOAuthService(apiName);
  oauthConfig.setConsumerKey("anonymous");
  oauthConfig.setConsumerSecret("anonymous");
  oauthConfig.setRequestTokenUrl("https://www.google.com/accounts/OAuthGetRequestToken?scope=" + encodeURI(SCOPES));
  oauthConfig.setAuthorizationUrl('https://accounts.google.com/OAuthAuthorizeToken');
  oauthConfig.setAccessTokenUrl('https://www.google.com/accounts/OAuthGetAccessToken'); 
  
  var optoins = {
    method : "get",
    oAuthServiceName : apiName,
    oAuthUseToken: "always",
  };
  
  //get profile.
  var res = UrlFetchApp.fetch("https://www.googleapis.com/plus/v1domains/people/" + USER_ID + "?key=" + API_KEY ,optoins);
  
  Logger.log(res.getContentText());
  var messagePostOptions = {
    method : "post",
    oAuthServiceName : apiName,
    oAuthUseToken: "always",
    contentType : "application/json",
    payload : JSON.stringify({
      "object": {
        "originalContent": "post from gas!!!"
      },
      "access": {
        "domainRestricted": true
      }
    })
  };
  //post activity.
  res = UrlFetchApp.fetch("https://www.googleapis.com/plus/v1domains/people/me/activities?key=" + API_KEY , messagePostOptions);
  
  Logger.log(res.getContentText());
}

When we I added "apiKey" and I received this kind of error "Uncaught ReferenceError: ScriptProperties is not defined".
Could you please let me know that what I have to do?