How to Reference Trello JavaScript Library in Google Apps Script: A Guide for Google Spreadsheets

Table of Contents#

1. Prerequisites
2. Why Not Directly Reference the Trello JS Library?
3. Understanding the Trello REST API
4. Step 1: Set Up Trello API Authentication
5. Step 2: Making Trello API Requests in Google Apps Script
6. Step 3: Building a Trello API Wrapper for GAS
7. Practical Examples: Syncing Google Sheets and Trello
   • Example 1: Create a Trello Card When a New Row is Added to Google Sheets
   • Example 2: Fetch Trello Cards and Update Google Sheets
8. Troubleshooting Common Issues
9. Best Practices
10. References

Prerequisites#

Before diving in, ensure you have:

• A Trello account.
• A Google account with access to Google Sheets and Google Apps Script.
• Basic familiarity with JavaScript and Google Apps Script (e.g., creating functions, using UrlFetchApp).
• A Trello board and list to test with (create one manually first for simplicity).

Why Not Directly Reference the Trello JS Library?#

Trello provides a client-side JavaScript library (trello.js) designed for web browsers. This library relies on browser-specific features (e.g., window object, CORS handling) and requires loading via <script> tags.

However, Google Apps Script runs on Google’s servers, not in a browser. It cannot load external client-side libraries directly. Instead, we use Trello’s REST API (a set of HTTP endpoints) to interact with Trello programmatically. This approach is server-side compatible and works seamlessly with GAS’s UrlFetchApp service for making HTTP requests.

Understanding the Trello REST API#

Trello’s REST API allows you to read and modify Trello resources (boards, lists, cards, etc.) via HTTP requests. Key endpoints include:

• GET /1/boards/{idBoard}: Fetch a board’s details.
• GET /1/lists/{idList}/cards: Fetch cards in a list.
• POST /1/cards: Create a new card.
• PUT /1/cards/{idCard}: Update a card (e.g., change status).

All requests require authentication (via an API key and token), and responses are returned in JSON format.

Step 1: Set Up Trello API Authentication#

To use the Trello API, you need two credentials: an API key (to identify your app) and a token (to authenticate your Trello account).

Step 1.1: Get Your Trello API Key#

1. Go to the Trello Developer Portal.
2. Log in with your Trello account.
3. Click Create new app (or use an existing app).
4. Name your app (e.g., "Google Sheets Sync") and add a description.
5. Under "API Key", copy your unique key (e.g., abc123def456).

Step 1.2: Generate a Trello Token#

Your token grants GAS permission to act on your behalf. To generate one:

1. From your app page, scroll to "Token" and click Generate a Token.
2. In the popup, review the permissions (ensure "Read" and "Write" access are enabled if you plan to create/update cards).
3. Click Allow to generate your token (e.g., xyz789...).

Step 1.3: Store Credentials Securely in GAS#

Never hardcode API keys/tokens in your script! Instead, store them in GAS Script Properties:

1. Open your Google Sheet, then click Extensions > Apps Script to open the GAS editor.
2. In the GAS editor, go to File > Project properties > Script properties.
3. Click Add row and add:
   • Name: TRELLO_API_KEY, Value: (your API key).
   • Name: TRELLO_TOKEN, Value: (your token).

Step 2: Making Trello API Requests in Google Apps Script#

Use GAS’s UrlFetchApp.fetch() to send HTTP requests to Trello’s API. Here’s a breakdown of the request structure:

Request Format#

const baseUrl = "https://api.trello.com/1";  
const apiKey = PropertiesService.getScriptProperties().getProperty("TRELLO_API_KEY");  
const token = PropertiesService.getScriptProperties().getProperty("TRELLO_TOKEN");  
 
// Example: Fetch a board by ID  
function fetchTrelloBoard(boardId) {  
  const url = `${baseUrl}/boards/${boardId}?key=${apiKey}&token=${token}`;  
  const response = UrlFetchApp.fetch(url);  
  const board = JSON.parse(response.getContentText());  
  return board;  
}  

Key Components:#

• Base URL: https://api.trello.com/1 (all endpoints start with this).
• Query Parameters: Append ?key={apiKey}&token={token} to authenticate.
• HTTP Methods: Use method in UrlFetchApp options for POST/PUT (default is GET).

Step 3: Building a Trello API Wrapper#

To simplify repeated API calls, create a reusable wrapper with helper functions. This abstracts low-level details (e.g., URL construction, error handling) and makes your code cleaner.

Example Wrapper Code#

const TRELLO_BASE_URL = "https://api.trello.com/1";  
 
function getTrelloAuthParams() {  
  return {  
    key: PropertiesService.getScriptProperties().getProperty("TRELLO_API_KEY"),  
    token: PropertiesService.getScriptProperties().getProperty("TRELLO_TOKEN")  
  };  
}  
 
// Generic function to fetch Trello data (GET request)  
function getTrelloData(endpoint, params = {}) {  
  const auth = getTrelloAuthParams();  
  const queryParams = new URLSearchParams({ ...auth, ...params }).toString();  
  const url = `${TRELLO_BASE_URL}${endpoint}?${queryParams}`;  
 
  try {  
    const response = UrlFetchApp.fetch(url);  
    return JSON.parse(response.getContentText());  
  } catch (e) {  
    console.error(`Error fetching Trello data: ${e.message}`);  
    throw e;  
  }  
}  
 
// Generic function to create/update Trello data (POST/PUT request)  
function modifyTrelloData(endpoint, method = "POST", data = {}) {  
  const auth = getTrelloAuthParams();  
  const payload = { ...auth, ...data };  
  const options = {  
    method: method,  
    payload: payload,  
    muteHttpExceptions: true // To handle non-200 responses  
  };  
 
  try {  
    const url = `${TRELLO_BASE_URL}${endpoint}`;  
    const response = UrlFetchApp.fetch(url, options);  
    const result = JSON.parse(response.getContentText());  
 
    if (response.getResponseCode() < 200 || response.getResponseCode() >= 300) {  
      throw new Error(`Trello API error: ${JSON.stringify(result)}`);  
    }  
    return result;  
  } catch (e) {  
    console.error(`Error modifying Trello data: ${e.message}`);  
    throw e;  
  }  
}  

Practical Examples: Syncing Google Sheets and Trello#

Let’s build real-world automations using the wrapper above.

Example 1: Create a Trello Card When a New Row is Added to Google Sheets#

Goal: When a user adds a new row to a Google Sheet (with task details), auto-create a Trello card in a specified list.

Step 1: Prepare Your Google Sheet#

Create a sheet with columns:

Step 2: Get Your Trello List ID#

To create a card, you need the ID of the Trello list where it will live:

1. Use the getTrelloData wrapper to fetch your board’s lists:

   function getTrelloLists(boardId) {  
     return getTrelloData(`/boards/${boardId}/lists`);  
   }  

2. Run getTrelloLists("your-board-id") (replace your-board-id with your board’s ID, found in the board’s URL: https://trello.com/b/{boardId}/...).
3. Find the list you want (e.g., "To Do") and copy its id (e.g., list123).

Step 3: Write the Automation Script#

Add this function to your GAS project to create a Trello card when a new row is added:

const TRELLO_LIST_ID = "your-list-id"; // Replace with your list ID  
 
function createTrelloCardFromSheet() {  
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();  
  const lastRow = sheet.getLastRow();  
  const rowData = sheet.getRange(lastRow, 1, 1, 4).getValues()[0]; // Get columns A-D  
 
  const [taskName, description, dueDate, status] = rowData;  
 
  // Only create if status is "To Do" and taskName is not empty  
  if (status === "To Do" && taskName) {  
    const cardData = {  
      name: taskName,  
      desc: description,  
      idList: TRELLO_LIST_ID,  
      due: dueDate ? new Date(dueDate).toISOString() : null  
    };  
 
    const newCard = modifyTrelloData("/cards", "POST", cardData);  
    console.log(`Created Trello card: ${newCard.name} (ID: ${newCard.id})`);  
 
    // Optional: Update Sheet with Trello card URL  
    sheet.getRange(lastRow, 5).setValue(newCard.shortUrl);  
  }  
}  

Step 4: Trigger the Function Automatically#

To run createTrelloCardFromSheet when a new row is added:

1. In the GAS editor, go to Edit > Current project’s triggers.
2. Click Add trigger.
3. Choose:
   • Choose which function to run: createTrelloCardFromSheet
   • Choose which deployment to run: Head
   • Select event source: From spreadsheet
   • Select event type: On change
4. Save the trigger.

Example 2: Fetch Trello Cards and Update Google Sheets#

Goal: Pull all cards from a Trello list and update a Google Sheet with their details (name, description, due date, status).

Script Code#

function syncTrelloCardsToSheet() {  
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Trello Cards"); // Create this sheet first  
  const listId = "your-list-id"; // Replace with your list ID  
 
  // Fetch cards from Trello list  
  const cards = getTrelloData(`/lists/${listId}/cards`);  
 
  // Clear existing data (keep header row)  
  sheet.getRange(2, 1, sheet.getLastRow() - 1, 4).clearContent();  
 
  // Write new data  
  const cardData = cards.map(card => [  
    card.name,  
    card.desc || "No description",  
    card.due ? new Date(card.due).toLocaleDateString() : "No due date",  
    card.idList // Replace with list name if needed (fetch list names first)  
  ]);  
 
  if (cardData.length > 0) {  
    sheet.getRange(2, 1, cardData.length, 4).setValues(cardData);  
  }  
  console.log(`Synced ${cards.length} cards to sheet`);  
}  

Run this manually or set a time-driven trigger (e.g., daily) to keep the sheet updated.

Troubleshooting Common Issues#

Authentication Errors#

• "Invalid key": Double-check your API key in Script Properties.
• "Invalid token": Regenerate your token (tokens can expire if revoked).

Permission Issues#

• If cards aren’t created, ensure your token has "Write" permissions (re-generate the token with write scope).

Rate Limits#

Trello’s API limits free accounts to ~100 requests/10 seconds. Use Utilities.sleep(1000) between bulk requests to avoid 429 (Too Many Requests) errors.

Parsing Errors#

• Always wrap JSON.parse() in a try-catch block to handle malformed responses.
• Use muteHttpExceptions: true in modifyTrelloData to inspect error details (e.g., response.getResponseCode()).

Best Practices#

1. Secure Credentials: Use Script Properties (not hardcoded values) to store API keys/tokens.
2. Limit Permissions: Generate a token with the minimum required scopes (e.g., read only if you don’t need to write data).
3. Handle Errors: Use try-catch blocks and log errors with console.error().
4. Test Incrementally: Test small parts (e.g., fetching a list) before building full automations.
5. Document Code: Add comments to explain endpoints, parameters, and triggers.

References#

• Trello REST API Documentation
• Google Apps Script UrlFetchApp Guide
• Trello Developer Portal
• Google Apps Script Triggers

By following this guide, you can seamlessly connect Google Sheets and Trello, automating workflows and reducing manual effort. The key is leveraging Trello’s REST API with Google Apps Script’s UrlFetchApp—no client-side libraries required! 🚀