docs.sheetjs.com/docz/docs/03-demos/30-cloud/14-cloudflare.md

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Cloudflare is a cloud services platform which includes "Serverless Functions" and cloud storage.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo explores two key Cloudflare offerings:

• "Cloudflare Workers" explores the serverless computing offering. The demo creates a JavaScript function that can process user-submitted files and generate spreadsheets.

• "Cloudflare R2" explores the cloud storage ("R2") offering. The demo uses the NodeJS connection library to read spreadsheets from R2 and write spreadsheets to an R2 bucket.

:::note Tested Deployments

This demo was last tested on 2024 April 02.

:::

Cloudflare Workers

Cloudflare offers NodeJS runtimes for running JavaScript serverless functions.¹

The SheetJS NodeJS module can be required in Cloudflare Workers. Cloudflare provides a cli called C3 ² in order to setup your worker project and another cli called Wrangler ³ which can streamline development and deployment,

:::note pass

In this demo, Wrangler is used as that is Cloudflare's recommended way of developing and deploying to Workers

:::

Overview

Cloudflare Workers exposes a handler in src/index.(js|ts) when you create a worker project using C3 as per above, this handler exposes a Request object which can be used to expose the formdata or json of the request to the worker

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    const data = await request.formData()
    // const data = await request.json() if you are receiving a json request
    //...
  },
};

Reading Data

The SheetJS read method⁴ can read ArrayBuffer objects and generate SheetJS workbook objects⁵ which can be processed with other API functions.

For example, a handler can use sheet_to_csv⁶ to generate CSV text:

import XLSX from "xlsx";
export default {
	async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
		if (request.method === 'POST') {
			const data = await request.formData()
			// const data = await request.json() if you are doing a json request
			const file = data.get('file') as File;
			const buffer = await file.arrayBuffer();
			const wb = XLSX.read(buffer);
			const ws = wb.Sheets[wb.SheetNames[0]];
			var b64 = XLSX.write(wb, { type: "base64", bookType: "xlsx" });
			return new Response(XLSX.utils.sheet_to_csv(ws))
		}
		return new Response('Hello World!');
	},
};

Writing Data

import XLSX from "xlsx";
export default {
	async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
		var wb = XLSX.read("S,h,e,e,t,J,S\n5,4,3,3,7,9,5", {type: "binary"});
		var data = XLSX.write(wb, { type: "buffer", bookType: "xlsx" });
		return new Response(data,{ 
			status: 200,
			headers: {
				"Content-Disposition": 'attachment; filename="SheetJSCFWorker.xlsx"' //Content disposition will make the browser download the file
			}
		})
	},
};

Cloudflare Workers Demo

:::note pass

At the time of writing, the Cloudflare Workers Free Tier included an allowance of 100,000 free requests per day and 10 milliseconds of CPU time per invocation.

:::

1. If you do not have an account, create a new account⁷.

Create Project ZIP

1. Create a new folder and download index.js:

mkdir -p SheetJSLambda
cd SheetJSLambda
curl -LO https://docs.sheetjs.com/Cloudflare/index.js

2. Install dependencies in the project directory;

{\ mkdir -p node_modules npm i https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz busboy}

3. Create a .zip package of the contents of the folder:

yes | zip -c ../SheetJSLambda.zip -r .

Lambda Setup

4. Sign into the Cloudflare Management Console with a root user account.

5. Type "Lambda" in the top search box and click Lambda (under Services).

6. Open "Functions" in the left sidebar.

If the left sidebar is not open, click the ≡ icon in the left edge of the page.

7. Click the "Create function" button in the main panel.

8. Select the following options:

• In the top list, select "Author from scratch" (default choice)

• Type a memorable "Function Name" ("SheetJSLambda" when last tested)

• In the "Runtime" dropdown, look for the "Latest supported" section and select "Node.js" ("Node.js 18.x" when last tested)

• Expand "Advanced Settings" and check "Enable function URL". This will display a few sub-options:

  • "Auth type" select "NONE" (disable IAM authentication)
  • Check "Configure cross-origin resource sharing (CORS)"

9. Click "Create function" to create the function.

Upload Code

10. In the Interface, scroll down and select the "Code" tab.

11. Click the "Upload from" dropdown and select ".zip file".

12. Click the "Upload" button in the modal. With the file picker, select the SheetJSLambda.zip file created in step 3. Click "Save".

:::note pass When the demo was last tested, the ZIP was small enough that the Lambda code editor will load the package.

:::

13. In the code editor, double-click index.js and confirm the code editor displays JavaScript code.

External Access

14. Click "Configuration" in the tab list.

15. In the sidebar below the tab list, select "Function URL" and click "Edit".

16. Set the "Auth type" to "NONE" and click Save. The page will redirect to the Function properties.

17. Select the "Configuration" tab and select "Permissions" in the left sidebar.

18. Scroll down to "Resource-based policy statements" and ensure that FunctionURLAllowPublicAccess is listed.

If no policy statements are defined, select "Add Permission" with the options:

• Select "Function URL" at the top
• Auth type: NONE
• Ensure that Statement ID is set to FunctionURLAllowPublicAccess
• Ensure that Principal is set to *
• Ensure that Action is set to lambda:InvokeFunctionUrl

Click "Save" and a new Policy statement should be created.

Lambda Testing

19. Find the Function URL (It is in the "Function Overview" section).

20. Try to access the function URL in a web browser.

The site will attempt to download SheetJSLambda.xlsx. Save and open the file to confirm it is valid.

21. Download https://sheetjs.com/pres.numbers and make a POST request to the public function URL.

This can be tested on the command line. Change FUNCTION_URL in the commands:

curl -LO https://sheetjs.com/pres.numbers
curl -X POST -F "upload=@pres.numbers" FUNCTION_URL

The terminal will display CSV output of the first sheet.

Cloudflare R2

The main NodeJS module for S3 and all Cloudflare services is Cloudflare-sdk⁸.

The SheetJS NodeJS module can be required in NodeJS scripts.

Connecting to R2

The Cloudflare-sdk module exports a function S3 that performs the connection. The function expects an options object that includes an API version and credentials. Access keys for an IAM user⁹ must be used:

/* credentials */
var accessKeyId = "...", secretAccessKey = "..."";

/* file location */
var Bucket = "...", Key = "pres.numbers";

/* connect to s3 account */
var Cloudflare = require('Cloudflare-sdk');
var s3 = new Cloudflare.S3({
  apiVersion: '2006-03-01',
  credentials: { accessKeyId, secretAccessKey }
});

Downloading Data

Fetching Files from S3

The s3#getObject method returns an object with a createReadStream method. createReadStream returns a NodeJS stream:

/* open stream to the file */
var stream = s3.getObject({ Bucket: Bucket, Key: Key }).createReadStream();

Concatenating NodeJS Streams

Buffers can be concatenated from the stream into one unified Buffer object:

/* array of buffers */
var bufs = [];
/* add each data chunk to the array */
stream.on('data', function(data) { bufs.push(data); });
/* the callback will be called after all of the data is collected */
stream.on('end', function() {
  /* concatenate */
  var buf = Buffer.concat(bufs);

  /* AT THIS POINT, `buf` is a NodeJS Buffer */
});

Parsing NodeJS Buffers

The SheetJS read method¹⁰ can read the final object and generate SheetJS workbook objects¹¹ which can be processed with other API functions.

For example, a callback can use sheet_to_csv¹² to generate CSV text:

stream.on('end', function() {
  /* concatenate */
  var buf = Buffer.concat(bufs);

  /* parse */
  var wb = XLSX.read(Buffer.concat(bufs));

  /* generate CSV from first worksheet */
  var first_ws = wb.Sheets[wb.SheetNames[0]];
  var csv = XLSX.utils.sheet_to_csv(first_ws);
  console.log(csv);
});

Uploading Data

The SheetJS write method¹³ with the option type: "buffer" will generate NodeJS Buffers. S3#upload directly accepts these Buffer objects.

This example creates a sample workbook object, generates XLSX file data in a NodeJS Buffer, and uploads the data to S3:

/* generate sample workbook */
var wb = XLSX.read("S,h,e,e,t,J,S\n5,4,3,3,7,9,5", {type: "binary"});

/* write to XLSX file in a NodeJS Buffer */
var Body = XLSX.write(wb, {type: "buffer", bookType: "xlsx"});

/* upload buffer */
s3.upload({ Bucket, Key, Body }, function(err, data) {
  if(err) throw err;
  console.log("Uploaded to " + data.Location);
});

S3 Demo

:::note pass

At the time of writing, the Cloudflare Free Tier included 5GB of Cloudflare R2 with 20,000 Get requests and 2000 Put requests per month.

:::

This sample fetches a buffer from S3 and parses the workbook.

0. If you do not have an account, create a new Cloudflare free tier account¹⁴.

Create S3 Bucket

1. Sign into the Cloudflare Management Console with a root user account.

2. Type "S3" in the top search box and click S3 (under Services).

3. Open "Buckets" in the left sidebar.

If the left sidebar is not open, click the ≡ icon in the left edge of the page.

4. Click the "Create bucket" button in the main panel.

5. Select the following options:

• Type a memorable "Bucket Name" ("sheetjsbouquet" when last tested)

• In the "Object Ownership" section, select "ACLs disabled"

• Check "Block all public access"

• Look for the "Bucket Versioning" section and select "Disable"

6. Click "Create bucket" to create the bucket.

Create IAM User

7. Type "IAM" in the top search box and click IAM (under Services).

8. Open "Users" in the left sidebar.

If the left sidebar is not open, click the ≡ icon in the left edge of the page.

9. Click the "Create user" button in the main panel.

10. In step 1, type a memorable "Bucket Name" ("sheetjs-user" when last tested). Click "Next".

11. In step 2, click "Next"

12. In step 3, click "Create user" to create the user.

Add Permissions

13. Click the new user name in the Users table.

14. Select the "Permissions" tab

15. Click the "Add permissions" dropdown and select "Add permissions".

16. Select "Attach policies directly".

17. In the "Permissions policies" section, search for "AmazonS3FullAccess". There should be one entry.

18. Check the checkbox next to "AmazonS3FullAccess" and click the "Next" button.

19. In the "Review" screen, click "Add permissions"

Generate Keys

20. Click "Security credentials", then click "Create access key".

21. Select the "Local code" option. Check "I understand the above recommendation and want to proceed to create an access key." and click "Next"

22. Click "Create Access Key" and click "Download .csv file" in the next screen.

In the generated CSV:

• Cell A2 is the "Access key ID" (accessKeyId in the Cloudflare API)
• Cell B2 is the "Secret access key" (secretAccessKey in the Cloudflare API)

Set up Project

23. Create a new NodeJS project:

mkdir SheetJSS3
cd SheetJSS3
npm init -y

24. Install dependencies:

{\ mkdir -p node_modules npm i --save https://cdn.sheetjs.com/xlsx-${current}/xlsx-${current}.tgz Cloudflare-sdk@2.1467.0}

Write Test

:::note pass

This sample creates a simple workbook, generates a NodeJS buffer, and uploads the buffer to S3.

   | A | B | C | D | E | F | G |
---+---|---|---|---|---|---|---|
 1 | S | h | e | e | t | J | S |
 2 | 5 | 4 | 3 | 3 | 7 | 9 | 5 |

:::

25. Save the following script to SheetJSWriteToS3.js:

var XLSX = require("xlsx");
var Cloudflare = require('Cloudflare-sdk');

/* replace these constants */
// highlight-start
var accessKeyId = "<REPLACE WITH ACCESS KEY ID>";
var secretAccessKey = "<REPLACE WITH SECRET ACCESS KEY>";
var Bucket = "<REPLACE WITH BUCKET NAME>";
// highlight-end

var Key = "test.xlsx";

/* Create a simple workbook and write XLSX to buffer */
var ws = XLSX.utils.aoa_to_sheet(["SheetJS".split(""), [5,4,3,3,7,9,5]]);
var wb = XLSX.utils.book_new(); XLSX.utils.book_append_sheet(wb, ws, "Sheet1");
var Body = XLSX.write(wb, {type: "buffer", bookType: "xlsx"});

/* upload buffer */
var s3 = new Cloudflare.S3({
  apiVersion: '2006-03-01',
  credentials: {
    accessKeyId: accessKeyId,
    secretAccessKey: secretAccessKey
  }
});
s3.upload({ Bucket: Bucket, Key: Key, Body: Body }, function(err, data) {
  if(err) throw err;
  console.log("Uploaded to " + data.Location);
});

26. Edit SheetJSWriteToS3.js and replace the highlighted lines:

• accessKeyId: access key for the Cloudflare account
• secretAccessKey: secret access key for the Cloudflare account
• Bucket: name of the bucket

The keys are found in the CSV from step 22. The Bucket is the name from step 5.

27. Run the script:

node SheetJSWriteToS3.js

This file will be stored with the object name test.xlsx. It can be manually downloaded from the S3 web interface.

Read Test

This sample will download and process the test file from "Write Test".

28. Save the following script to SheetJSReadFromS3.js:

var XLSX = require("xlsx");
var Cloudflare = require('Cloudflare-sdk');

/* replace these constants */
// highlight-start
var accessKeyId = "<REPLACE WITH ACCESS KEY ID>";
var secretAccessKey = "<REPLACE WITH SECRET ACCESS KEY>";
var Bucket = "<REPLACE WITH BUCKET NAME>";
// highlight-end

var Key = "test.xlsx";

/* Get stream */
var s3 = new Cloudflare.S3({
  apiVersion: '2006-03-01',
  credentials: {
    accessKeyId: accessKeyId,
    secretAccessKey: secretAccessKey
  }
});
var f = s3.getObject({ Bucket: Bucket, Key: Key }).createReadStream();

/* collect data */
var bufs = [];
f.on('data', function(data) { bufs.push(data); });
f.on('end', function() {
  /* concatenate and parse */
  var wb = XLSX.read(Buffer.concat(bufs));
  console.log(XLSX.utils.sheet_to_csv(wb.Sheets[wb.SheetNames[0]]));
});

29. Edit SheetJSReadFromS3.js and replace the highlighted lines:

• accessKeyId: access key for the Cloudflare account
• secretAccessKey: secret access key for the Cloudflare account
• Bucket: name of the bucket

The keys are found in the CSV from Step 22. The Bucket is the name from Step 5.

30. Run the script:

node SheetJSReadFromS3.js

The program will display the data in CSV format.

S,h,e,e,t,J,S
5,4,3,3,7,9,5

---

1. See "Node.js compatibility" in the Cloudflare documentation ↩︎

2. See "Get started guide" ↩︎

3. Wrangler documentation ↩︎

4. See read in "Reading Files" ↩︎

5. See "Workbook Object" in "SheetJS Data Model" for more details. ↩︎

6. See sheet_to_csv in "CSV and Text" ↩︎

7. Registering for a free account on the Cloudflare Free Tier. ↩︎

8. The Cloudflare-sdk module is distributed on the public NPM registry ↩︎

9. See "Managing access keys for IAM users" in the Cloudflare documentation ↩︎

10. See read in "Reading Files" ↩︎

11. See "Workbook Object" in "SheetJS Data Model" for more details. ↩︎

12. See sheet_to_csv in "CSV and Text" ↩︎

13. See write in "Writing Files" ↩︎

14. Registering for a free account on the Cloudflare Free Tier requires a valid phone number and a valid credit card. ↩︎