Yagisanatode/Index.html

## appsscript.json
{
  "timeZone": "Australia/Hobart",
  "dependencies": {},
  "exceptionLogging": "STACKDRIVER",
  "runtimeVersion": "V8",
  "webapp": {
    "executeAs": "USER_ACCESSING",
    "access": "ANYONE"
  }
}

## Index.html
<!DOCTYPE html>
<html>
  <head>
    <base target="_top">
  </head>
  <body>
    <h1 style="color:blue">You are worthy!</h1>
  </body>
</html>

## NonUser.html
<!DOCTYPE html>
<html>
  <head>
    <base target="_top">
  </head>
  <body>
    <h1 style="color:red">You are not worthy!</h1>
  </body>
</html>

## webApp.gs
// ################################## VALIDATE USERS ON A WEB APP ##################################
// Allows users with a Gmail or Domain Google Workspace account to be validated and given access to
// a WebApp.
// Can be easily be adapted for Google Workspace Editor Add-on Side-bars and Dialogue Boxes
// @author Yagisanatode
// You can check out the full write up here: {@link https://yagisanatode.com/2021/08/18/how-to-validate-specific-users-on-a-web-app-in-google-apps-scripts}
// #################################################################################################

//##### GLOBALS #####
FILE_ID = '1JYq_HX_zCqyGYJzWtAkpIoVruPVAqYKDfKYW9F0A92o'

//####################### Create Webpage for Webapp ############################
/**Creates webpage for web app.
 * First calls validators to check if user has edit access to selected file as
 * either an individual user or a group.
 * Builds 'Index' file if user has access otherwise builds 'NonUser' file.
 */
function doGet() {
  const userEmail = Session.getActiveUser().getEmail()
  const fileID = FILE_ID;

  const isValid = validate(userEmail, fileID)
  let htmlfile = (isValid)? 'Index':'NonUser';


  const html = HtmlService.createTemplateFromFile(htmlfile)
    .evaluate()
    .setTitle("The Worthy")
    .setXFrameOptionsMode(HtmlService.XFrameOptionsMode.ALLOWALL)
    .addMetaTag('viewport', 'width=device-width, initial-scale=1');

  return html;
};


/**
 * Checks if user is an editor of a file.
 * First checks email, then check if member of group.
 * @param {string} email - email address of active user.
 * @param {string} fileID - the connected file ID with the shared editors.
 * @returns {boolean} true if user is and editor of file. Otherwise, false.
 */
function validate(email, fileID){
  let isValid = false; //Indicates if email is an editor.

  /**
   * Get's  list of file editors by email.
   * @returns {array} list of emails of all editors in file
   */
  const emailList = (()=>{
    var file;
    try{
      file = DriveApp.getFileById(fileID);

    }catch(e){

      return false; // If user has no access.
    }

    return file.getEditors().map(editor => {
      return editor.getEmail();
    })
  })();


  if(!emailList){
    isValid = false;
    return isValid;
  }

  /**
   * Get's list any group email with edit permission that
   * the user is a memeber of.
   * @returns {boolean} true if match.
   */
  const groupEmailList = (()=>{

    let isMemberOfGroup = false;

    GroupsApp.getGroups().map(group => {
      return group.getEmail()
    }).forEach(group => {
      if (emailList.includes(group)) {
        isMemberOfGroup = true
      }
    })
    return isMemberOfGroup;
  })()

  //Check if email in editor list.
  if(emailList.includes(email)){
    isValid = true;
  }else if(groupEmailList){
    isValid = true;
  }

  return isValid;

}
	{
	"timeZone": "Australia/Hobart",
	"dependencies": {},
	"exceptionLogging": "STACKDRIVER",
	"runtimeVersion": "V8",
	"webapp": {
	"executeAs": "USER_ACCESSING",
	"access": "ANYONE"
	}
	}
	<!DOCTYPE html>
	<html>
	<head>
	<base target="_top">
	</head>
	<body>
	<h1 style="color:blue">You are worthy!</h1>
	</body>
	</html>
	// ################################## VALIDATE USERS ON A WEB APP ##################################
	// Allows users with a Gmail or Domain Google Workspace account to be validated and given access to
	// a WebApp.
	// Can be easily be adapted for Google Workspace Editor Add-on Side-bars and Dialogue Boxes
	// @author Yagisanatode
	// You can check out the full write up here: {@link https://yagisanatode.com/2021/08/18/how-to-validate-specific-users-on-a-web-app-in-google-apps-scripts}
	// #################################################################################################

	//##### GLOBALS #####
	FILE_ID = '1JYq_HX_zCqyGYJzWtAkpIoVruPVAqYKDfKYW9F0A92o'

	//####################### Create Webpage for Webapp ############################
	/**Creates webpage for web app.
	* First calls validators to check if user has edit access to selected file as
	* either an individual user or a group.
	* Builds 'Index' file if user has access otherwise builds 'NonUser' file.
	*/
	function doGet() {
	const userEmail = Session.getActiveUser().getEmail()
	const fileID = FILE_ID;

	const isValid = validate(userEmail, fileID)
	let htmlfile = (isValid)? 'Index':'NonUser';


	const html = HtmlService.createTemplateFromFile(htmlfile)
	.evaluate()
	.setTitle("The Worthy")
	.setXFrameOptionsMode(HtmlService.XFrameOptionsMode.ALLOWALL)
	.addMetaTag('viewport', 'width=device-width, initial-scale=1');

	return html;
	};


	/**
	* Checks if user is an editor of a file.
	* First checks email, then check if member of group.
	* @param {string} email - email address of active user.
	* @param {string} fileID - the connected file ID with the shared editors.
	* @returns {boolean} true if user is and editor of file. Otherwise, false.
	*/
	function validate(email, fileID){
	let isValid = false; //Indicates if email is an editor.

	/**
	* Get's list of file editors by email.
	* @returns {array} list of emails of all editors in file
	*/
	const emailList = (()=>{
	var file;
	try{
	file = DriveApp.getFileById(fileID);

	}catch(e){

	return false; // If user has no access.
	}

	return file.getEditors().map(editor => {
	return editor.getEmail();
	})
	})();


	if(!emailList){
	isValid = false;
	return isValid;
	}

	/**
	* Get's list any group email with edit permission that
	* the user is a memeber of.
	* @returns {boolean} true if match.
	*/
	const groupEmailList = (()=>{

	let isMemberOfGroup = false;

	GroupsApp.getGroups().map(group => {
	return group.getEmail()
	}).forEach(group => {
	if (emailList.includes(group)) {
	isMemberOfGroup = true
	}
	})
	return isMemberOfGroup;
	})()

	//Check if email in editor list.
	if(emailList.includes(email)){
	isValid = true;
	}else if(groupEmailList){
	isValid = true;
	}

	return isValid;

	}