Gas Developer

GAS Developer

Build Google Apps Script solutions for Spreadsheet automation, Gmail, Calendar, and Drive integration.

Instructions

1. Understand the requirement: What Google service? What automation? What trigger?

2. Choose the right approach:

   Use Case	Service	Trigger
   Data processing	Spreadsheet	onEdit / time-driven
   Email automation	Gmail	time-driven
   Calendar sync	Calendar	time-driven / onChange
   File management	Drive	time-driven
   Form processing	Forms	onFormSubmit
   Web dashboard	HTML Service	doGet

3. Write clean GAS code following best practices below.

4. Test thoroughly — use Logger.log() for debugging.

5. Document the setup — triggers, permissions, configuration.

Templates

Spreadsheet — Read/Write

function processSheet() {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const sheet = ss.getSheetByName('Data');
  const data = sheet.getDataRange().getValues();
  
  // Skip header row
  for (let i = 1; i < data.length; i++) {
    const [name, email, status] = data[i];
    if (status === '') {
      // Process row
      sheet.getRange(i + 1, 3).setValue('Processed');
    }
  }
}

Gmail — Send with Template

function sendTemplateEmail(to, subject, templateName) {
  const template = HtmlService.createTemplateFromFile(templateName);
  const htmlBody = template.evaluate().getContent();
  
  GmailApp.sendEmail(to, subject, '', {
    htmlBody: htmlBody,
    name: 'Your Name'
  });
}

External API Call

function callExternalApi(endpoint, apiKey) {
  const options = {
    method: 'get',
    headers: { 'Authorization': 'Bearer ' + apiKey },
    muteHttpExceptions: true
  };
  
  const response = UrlFetchApp.fetch(endpoint, options);
  const code = response.getResponseCode();
  
  if (code !== 200) {
    Logger.log('API error: ' + code + ' ' + response.getContentText());
    return null;
  }
  
  return JSON.parse(response.getContentText());
}

Time-Driven Trigger Setup

function createDailyTrigger() {
  // Delete existing triggers for this function
  const triggers = ScriptApp.getProjectTriggers();
  triggers.forEach(t => {
    if (t.getHandlerFunction() === 'dailyTask') {
      ScriptApp.deleteTrigger(t);
    }
  });
  
  // Create new daily trigger at 9 AM
  ScriptApp.newTrigger('dailyTask')
    .timeBased()
    .atHour(9)
    .everyDays(1)
    .create();
}

Error Handling Pattern

function safeExecute(fn, context) {
  try {
    return fn();
  } catch (error) {
    Logger.log('Error in ' + context + ': ' + error.message);
    // Optional: send error notification
    GmailApp.sendEmail('admin@example.com', 
      'GAS Error: ' + context, error.stack);
    return null;
  }
}

Best Practices

• Batch operations: Use getValues() / setValues() instead of cell-by-cell
• Quota awareness: GAS has daily quotas (email: 100/day free, URL fetch: 20,000/day)
• Cache: Use CacheService for expensive API calls
• Properties: Store config in PropertiesService (not hardcoded)
• Lock: Use LockService to prevent concurrent trigger execution

Security

• Never hardcode API keys — use PropertiesService.getScriptProperties()
• Validate user input — especially in web apps (doGet/doPost)
• Limit sharing — deploy as "Execute as me, accessible to specific users"
• Review permissions — GAS requests broad OAuth scopes; explain to client

Delivery Checklist

□ Code tested with sample data
□ Triggers documented and set up
□ Error handling in place
□ Setup instructions included
□ API keys stored in Properties (not code)
□ Permissions explained to client

Requirements

• Google account with Apps Script access
• No local dependencies — runs entirely in Google Cloud