Bundling Sheets with SystemJS

SystemJS¹ is a module loader for NodeJS and browsers.

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

This demo uses SystemJS and SheetJS to export data. We'll explore two workflows:

• "Browser" explores how to load SheetJS with SystemJS using the in-browser dynamic loader

• "NodeJS" explores how to load SheetJS with SystemJS in NodeJS.

This demo was originally written for SystemJS 0.19, the most popular SystemJS version used with Angular projects. In the years since the release, Angular and other tools using SystemJS have switched to Webpack.

This demo focuses on integration details with the SystemJS loader.

The demos follow the "Export Tutorial", which covers SheetJS library usage in more detail.

Tested Deployments

This demo was tested in the following environments:

Version	Platform	Date
0.19.47	NodeJS	2024-03-31
0.20.16	Browser	2024-03-31
0.20.19	NodeJS	2024-03-31
0.21.6	NodeJS	2024-03-31
6.14.3	NodeJS	2024-03-31

Browser

The Live demo loads SystemJS from the CDN, uses it to load the standalone script from the SheetJS CDN and emulate a require implementation when loading main.js

"View Source" works on the main HTML page and the main.js script.

SystemJS fails by default because the library does not export anything in the web browser. The meta configuration option can be used to expose XLSX:

SystemJS.config({
  meta: {
    'xlsx': {
      exports: 'XLSX' // <-- tell SystemJS to expose the XLSX variable
    }
  },
  map: {
    'xlsx': 'https://cdn.sheetjs.com/xlsx-0.20.3/package/dist/xlsx.full.min.js',
    'fs': '',     // <--|
    'crypto': '', // <--| suppress native node modules
    'stream': ''  // <--|
  }
});
SystemJS.import('main.js'); // load `main.js`

With this import, the main.js script can freely require("xlsx").

Web Workers

Web Workers can load the SystemJS library with importScripts, but the imported code cannot assign the original worker's onmessage callback. The recommended approach is to expose a global from the required script, For example, supposing the shared name is _cb, the primary worker script would call the callback:

worker.js

/* main worker script */
importScripts('system.js');

SystemJS.config({ /* ... browser config ... */ });

onmessage = function(evt) {
  SystemJS.import('workermain.js').then(function() { _cb(evt); });
};

The worker script would define and expose the function:

workermain.js

/* Loaded with SystemJS import */
var XLSX = require('xlsx');

_cb = function(evt) { /* ... do work here ... */ };

NodeJS

It is strongly recommended to use the NodeJS require method when possible.

This demo is relevant for legacy projects that use the SystemJS NodeJS loader.

Old Style

The NodeJS module main script is xlsx/xlsx.js and should be mapped:

SystemJS.config({
  map: {
    "xlsx": "./node_modules/xlsx/xlsx.js"
  }
});

The standalone scripts can be required, but SystemJS config must include a hint that the script assigns a global:

SystemJS.config({
  meta: {
    "standalone": { format: "global" }
  },
  map: {
    "standalone": "xlsx.full.min.js"
  }
});

New Style

Newer versions of SystemJS supports "import maps" through applyImportMap:

const SystemJS = require('systemjs');
const src = require("path").join(process.cwd(), 'node_modules/xlsx/xlsx.js');
SystemJS.applyImportMap(SystemJS.System, {
  imports: {
    'xlsx': "file://" + src,
    'fs': 'node:fs',
    'crypto': 'node:crypto',
    'stream': 'node:stream'
  }
});

In the modern style, importing to the name XLSX will cause conflicts.

It is strongly recommended to import to the name _XLSX!

SystemJS.System.import("xlsx").then(function(
  _XLSX // use _XLSX instead of XLSX
) {
  if(typeof XLSX == "undefined") throw "Import failed!";

  // XLSX is defined here
  console.log(XLSX.version);
});

NodeJS Demo

0. Prepare a blank project:

mkdir sheetjs-systemjs
cd sheetjs-systemjs
npm init -y

1. Install the dependencies:

npm i --save https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz [email protected]

2. Download SheetJSystem.js and move to the project folder:

curl -LO https://docs.sheetjs.com/systemjs/SheetJSystem.js

The script handles old-style and new-style SystemJS loaders.

3. Run in NodeJS:

node SheetJSystem.js

If the demo worked, Presidents.xlsx will be created.

As it uses fetch, this demo requires Node 18.

Footnotes

1. The project does not have a separate website. The source repository is hosted on GitHub ↩