# 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.

### Node Buffer

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

```js
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 */
});
```

### 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:

```bash
# upload test.xls and update data
curl -X POST -F "data=@test.xls" http://localhost:7262/
# download data in SYLK format
curl -X GET http://localhost:7262/?t=slk
# read sheetjs.xlsx from the server directory
curl -X POST http://localhost:7262/?f=sheetjs.xlsx
# 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:

```js
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.


## xlsx script with micro

The node module ships with the `xlsx` bin script.  For global installs, symlinks
are configured to enable running `xlsx` from anywhere.  For local installs, the
appropriate symlink is set up in `node_modules/.bin/`.

The `--arrays` option directs `xlsx` to generate an array of arrays that can be
parsed by the server.  To generate files, the `json2csv` module exports the JS
array of arrays to a CSV, the server writes the file, and the `xlsx` command is
used to generate files of different formats.