97 lines
3.3 KiB
Markdown
97 lines
3.3 KiB
Markdown
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# NodeJS Server Deployments
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This library is 100% pure JS. This is great for compatibility but tends to lock
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up long-running processes. In the web browser, Web Workers are used to offload
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work from the main browser thread. In NodeJS, there are other strategies. This
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demo shows a few different strategies applied to different server frameworks.
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NOTE: these examples merely demonstrate the core concepts and do not include
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appropriate error checking or other production-level features.
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### Node Buffer
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The `read` and `write` functions can handle `Buffer` data with `type:"buffer"`.
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For example, the `request` library returns data in a buffer:
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```js
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var XLSX = require('xlsx'), request = require('request');
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request(url, {encoding: null}, function(err, res, data) {
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if(err || res.statusCode !== 200) return;
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/* data is a node Buffer that can be passed to XLSX.read */
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var workbook = XLSX.read(data, {type:'buffer'});
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/* DO SOMETHING WITH workbook HERE */
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});
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```
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### Example servers
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Each example server is expected to hold an array-of-arrays in memory. They are
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expected to handle:
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- `POST / ` accepts an encoded `file` and updates the internal storage
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- `GET /?t=<type>` returns the internal storage in the specified type
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- `POST /?f=<name>` reads the local file and updates the internal storage
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- `GET /?f=<name>` writes the file to the specified name
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Testing with cURL is straightforward:
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```bash
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# upload test.xls and update data
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curl -X POST -F "data=@test.xls" http://localhost:7262/
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# download data in SYLK format
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curl -X GET http://localhost:7262/?t=slk
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# read sheetjs.xlsx from the server directory
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curl -X POST http://localhost:7262/?f=sheetjs.xlsx
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# write sheetjs.xlsb in the XLSB format
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curl -X GET http://localhost:7262/?f=sheetjs.xlsb
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```
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## Main-process logic with express
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The most straightforward approach is to handle the data directly in HTTP event
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handlers. The `buffer` type for `XLSX.read` and `XLSX.write` work with `http`
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module and with express directly. The following snippet generates a workbook
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based on an array of arrays and sends it to the client:
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```js
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function send_aoa_to_client(req, res, data, bookType) {
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/* generate workbook */
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var ws = XLSX.utils.aoa_to_sheet(data);
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var wb = XLSX.utils.book_new();
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XLSX.utils.book_append_sheet(wb, ws, "SheetJS");
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/* generate buffer */
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var buf = XLSX.write(wb, {type:'buffer', bookType:bookType || "xlsx"});
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/* send to client */
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res.status(200).send(buf);
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}
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```
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## fork with koa
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`child_process.fork` provides a light-weight and customizable way to offload
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work from the main server process. This demo passes commands to a custom child
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process and the child passes back buffers of data.
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The main server script is `koa.js` and the worker script is `koasub.js`. State
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is maintained in the worker script.
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## xlsx script with micro
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The node module ships with the `xlsx` bin script. For global installs, symlinks
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are configured to enable running `xlsx` from anywhere. For local installs, the
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appropriate symlink is set up in `node_modules/.bin/`.
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The `--arrays` option directs `xlsx` to generate an array of arrays that can be
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parsed by the server. To generate files, the `json2csv` module exports the JS
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array of arrays to a CSV, the server writes the file, and the `xlsx` command is
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used to generate files of different formats.
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