NodeJS Server Deployments

This library is 100% pure JS. This is great for compatibility but tends to lock up long-running processes. In the web browser, Web Workers are used to offload work from the main browser thread. In NodeJS, there are other strategies. This demo shows a few different strategies applied to different server frameworks.

NOTE: these examples merely demonstrate the core concepts and do not include appropriate error checking or other production-level features.

Express Setup

The following commands are required in order to test the Express demo:

npm install express printj xlsx express-formidable
node express.js

Koa Setup

The following commands are required in order to test the Koa demo:

npm install koa printj formidable xlsx
node koa.js

Hapi Setup

Note: Hapi demo as written only works with Hapi version 16 and below.

The following commands are required in order to test the Hapi demo:

npm install hapi@16.x printj tiny-worker xlsx
node hapi.js

Node Buffer

The read and write functions can handle Buffer data with type:"buffer". For example, the request library returns data in a buffer:

var XLSX = require('xlsx'), request = require('request');
request(url, {encoding: null}, function(err, res, data) {
    if(err || res.statusCode !== 200) return;

    /* data is a node Buffer that can be passed to XLSX.read */
    var workbook = XLSX.read(data, {type:'buffer'});

    /* DO SOMETHING WITH workbook HERE */
});

The readFile / writeFile functions wrap fs.{read,write}FileSync:

/* equivalent to `var wb = XLSX.readFile("sheetjs.xlsx");` */
var buf = fs.readFileSync("sheetjs.xlsx");
var wb = XLSX.read(buf, {type:'buffer'});

Responding to Form Uploads

Using formidable, files uploaded to forms are stored to temporary files that can be read with readFile:

/* within the server callback function(request, response) { */
var form = new formidable.IncomingForm();
form.parse(req, function(err, fields, files) {
    var f = files[Object.keys(files)[0]];
    var workbook = XLSX.readFile(f.path);
    /* DO SOMETHING WITH workbook HERE */
});

The node.js demo shows a plain HTTP server that accepts file uploads and converts data to requested output format.

Example servers

Each example server is expected to hold an array-of-arrays in memory. They are expected to handle:

• POST / accepts an encoded file and updates the internal storage
• GET /?t=<type> returns the internal storage in the specified type
• POST /?f=<name> reads the local file and updates the internal storage
• GET /?f=<name> writes the file to the specified name

Testing with cURL is straightforward:

# upload sheetjs.csv and update data
curl -X POST -F "data=@sheetjs.csv" http://localhost:7262/
# download data in SYLK format
curl -X GET http://localhost:7262/?t=slk
# read sheetjs.csv from the server directory
curl -X POST http://localhost:7262/?f=sheetjs.csv
# write sheetjs.xlsb in the XLSB format
curl -X GET http://localhost:7262/?f=sheetjs.xlsb

Main-process logic with express

The most straightforward approach is to handle the data directly in HTTP event handlers. The buffer type for XLSX.read and XLSX.write work with http module and with express directly. The following snippet generates a workbook based on an array of arrays and sends it to the client:

function send_aoa_to_client(req, res, data, bookType) {
    /* generate workbook */
    var ws = XLSX.utils.aoa_to_sheet(data);
    var wb = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, "SheetJS");

    /* generate buffer */
    var buf = XLSX.write(wb, {type:'buffer', bookType:bookType || "xlsx"});

    /* send to client */
    res.status(200).send(buf);
}

fork with koa

child_process.fork provides a light-weight and customizable way to offload work from the main server process. This demo passes commands to a custom child process and the child passes back buffers of data.

The main server script is koa.js and the worker script is koasub.js. State is maintained in the worker script.

tiny-worker with hapi

tiny-worker provides a Web Worker-like interface. Binary strings and simple objects are readily passed across the Worker divide.

The main server script is hapi.js and the worker script is worker.js. State is maintained in the server script.

Note: due to an issue with hapi payload parsing, the route POST /file is used to handle the case of reading from file, so the cURL test is:

# upload sheetjs.csv and update data
curl -X POST -F "data=@sheetjs.csv" http://localhost:7262/
# download data in SYLK format
curl -X GET http://localhost:7262/?t=slk
# read sheetjs.csv from the server directory
curl -X POST http://localhost:7262/file?f=sheetjs.csv
# write sheetjs.xlsb in the XLSB format
curl -X GET http://localhost:7262/?f=sheetjs.xlsb

NestJS

NestJS is a Node.js framework for server-side web applications.

This demo uses SheetJS to parse a spreadsheet via a POST API endpoint. The file arrives to the endpoint as body form-data, accessible using the file key. After parsing the file, CSV contents of the first worksheet will be returned. Body parsing uses multer.

Before running the demo, the NestJS CLI tool must be installed. The instruction is described in the NestJS "First Steps":

npm i -g @nestjs/cli
make nest

The demo can be tested using the /sheetjs/upload-xlsx-file endpoint:

curl -X POST -F "file=@test.xlsx" http://localhost:3000/sheetjs/upload-xlsx-file

The included nest.sh script creates and configures the project.

This demo creates a module and a controller. The controller handles the actual requests (creating the endpoint) while the module is used to configure multer.