xsheetjs/docbits/20_import.md

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## Acquiring and Extracting Data
### Parsing Workbooks
**API**
_Extract data from spreadsheet bytes_
```js
var workbook = XLSX.read(data, opts);
```
The `read` method can extract data from spreadsheet bytes stored in a JS string,
"binary string", NodeJS buffer or typed array (`Uint8Array` or `ArrayBuffer`).
_Read spreadsheet bytes from a local file and extract data_
```js
var workbook = XLSX.readFile(filename, opts);
```
The `readFile` method attempts to read a spreadsheet file at the supplied path.
Browsers generally do not allow reading files in this way (it is deemed a
security risk), and attempts to read files in this way will throw an error.
The second `opts` argument is optional. ["Parsing Options"](#parsing-options)
covers the supported properties and behaviors.
**Examples**
Here are a few common scenarios (click on each subtitle to see the code):
<details>
<summary><b>Local file in a NodeJS server</b> (click to show)</summary>
`readFile` uses `fs.readFileSync` under the hood:
```js
var XLSX = require("xlsx");
var workbook = XLSX.readFile("test.xlsx");
```
For Node ESM, the `readFile` helper is not enabled. Instead, `fs.readFileSync`
should be used to read the file data as a `Buffer` for use with `XLSX.read`:
```js
import { readFileSync } from "fs";
import { read } from "xlsx/xlsx.mjs";
const buf = readFileSync("test.xlsx");
/* buf is a Buffer */
const workbook = read(buf);
```
</details>
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<details>
<summary><b>Local file in a Deno application</b> (click to show)</summary>
`readFile` uses `Deno.readFileSync` under the hood:
```js
// @deno-types="https://deno.land/x/sheetjs/types/index.d.ts"
import * as XLSX from 'https://deno.land/x/sheetjs/xlsx.mjs'
const workbook = XLSX.readFile("test.xlsx");
```
Applications reading files must be invoked with the `--allow-read` flag. The
[`deno` demo](demos/deno/) has more examples
</details>
<details>
<summary><b>User-submitted file in a web page ("Drag-and-Drop")</b> (click to show)</summary>
For modern websites targeting Chrome 76+, `File#arrayBuffer` is recommended:
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```js
// XLSX is a global from the standalone script
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async function handleDropAsync(e) {
e.stopPropagation(); e.preventDefault();
const f = e.dataTransfer.files[0];
/* f is a File */
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const data = await f.arrayBuffer();
/* data is an ArrayBuffer */
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const workbook = XLSX.read(data);
/* DO SOMETHING WITH workbook HERE */
}
drop_dom_element.addEventListener("drop", handleDropAsync, false);
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```
For maximal compatibility, the `FileReader` API should be used:
```js
function handleDrop(e) {
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e.stopPropagation(); e.preventDefault();
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var f = e.dataTransfer.files[0];
/* f is a File */
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var reader = new FileReader();
reader.onload = function(e) {
var data = e.target.result;
/* reader.readAsArrayBuffer(file) -> data will be an ArrayBuffer */
var workbook = XLSX.read(data);
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/* DO SOMETHING WITH workbook HERE */
};
reader.readAsArrayBuffer(f);
}
drop_dom_element.addEventListener("drop", handleDrop, false);
```
<https://oss.sheetjs.com/sheetjs/> demonstrates the FileReader technique.
</details>
<details>
<summary><b>User-submitted file with an HTML INPUT element</b> (click to show)</summary>
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Starting with an HTML INPUT element with `type="file"`:
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```html
<input type="file" id="input_dom_element">
```
For modern websites targeting Chrome 76+, `Blob#arrayBuffer` is recommended:
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```js
// XLSX is a global from the standalone script
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async function handleFileAsync(e) {
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const file = e.target.files[0];
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const data = await file.arrayBuffer();
/* data is an ArrayBuffer */
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const workbook = XLSX.read(data);
/* DO SOMETHING WITH workbook HERE */
}
input_dom_element.addEventListener("change", handleFileAsync, false);
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```
For broader support (including IE10+), the `FileReader` approach is recommended:
```js
function handleFile(e) {
var file = e.target.files[0];
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var reader = new FileReader();
reader.onload = function(e) {
var data = e.target.result;
/* reader.readAsArrayBuffer(file) -> data will be an ArrayBuffer */
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var workbook = XLSX.read(e.target.result);
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/* DO SOMETHING WITH workbook HERE */
};
reader.readAsArrayBuffer(file);
}
input_dom_element.addEventListener("change", handleFile, false);
```
The [`oldie` demo](demos/oldie/) shows an IE-compatible fallback scenario.
</details>
<details>
<summary><b>Fetching a file in the web browser ("Ajax")</b> (click to show)</summary>
For modern websites targeting Chrome 42+, `fetch` is recommended:
```js
// XLSX is a global from the standalone script
(async() => {
const url = "http://oss.sheetjs.com/test_files/formula_stress_test.xlsx";
const data = await (await fetch(url)).arrayBuffer();
/* data is an ArrayBuffer */
const workbook = XLSX.read(data);
/* DO SOMETHING WITH workbook HERE */
})();
```
For broader support, the `XMLHttpRequest` approach is recommended:
```js
var url = "http://oss.sheetjs.com/test_files/formula_stress_test.xlsx";
/* set up async GET request */
var req = new XMLHttpRequest();
req.open("GET", url, true);
req.responseType = "arraybuffer";
req.onload = function(e) {
var workbook = XLSX.read(req.response);
/* DO SOMETHING WITH workbook HERE */
};
req.send();
```
The [`xhr` demo](demos/xhr/) includes a longer discussion and more examples.
<http://oss.sheetjs.com/sheetjs/ajax.html> shows fallback approaches for IE6+.
</details>
<details>
<summary><b>Local file in a PhotoShop or InDesign plugin</b> (click to show)</summary>
`readFile` wraps the `File` logic in Photoshop and other ExtendScript targets.
The specified path should be an absolute path:
```js
#include "xlsx.extendscript.js"
/* Read test.xlsx from the Documents folder */
var workbook = XLSX.readFile(Folder.myDocuments + "/test.xlsx");
```
The [`extendscript` demo](demos/extendscript/) includes a more complex example.
</details>
<details>
<summary><b>Local file in an Electron app</b> (click to show)</summary>
`readFile` can be used in the renderer process:
```js
/* From the renderer process */
var XLSX = require("xlsx");
var workbook = XLSX.readFile(path);
```
Electron APIs have changed over time. The [`electron` demo](demos/electron/)
shows a complete example and details the required version-specific settings.
</details>
<details>
<summary><b>Local file in a mobile app with React Native</b> (click to show)</summary>
The [`react` demo](demos/react) includes a sample React Native app.
Since React Native does not provide a way to read files from the filesystem, a
third-party library must be used. The following libraries have been tested:
- [`react-native-file-access`](https://npm.im/react-native-file-access)
The `base64` encoding returns strings compatible with the `base64` type:
```js
import XLSX from "xlsx";
import { FileSystem } from "react-native-file-access";
const b64 = await FileSystem.readFile(path, "base64");
/* b64 is a base64 string */
const workbook = XLSX.read(b64, {type: "base64"});
```
- [`react-native-fs`](https://npm.im/react-native-fs)
The `ascii` encoding returns binary strings compatible with the `binary` type:
```js
import XLSX from "xlsx";
import { readFile } from "react-native-fs";
const bstr = await readFile(path, "ascii");
/* bstr is a binary string */
const workbook = XLSX.read(bstr, {type: "binary"});
```
</details>
<details>
<summary><b>NodeJS Server File Uploads</b> (click to show)</summary>
`read` can accept a NodeJS buffer. `readFile` can read files generated by a
HTTP POST request body parser like [`formidable`](https://npm.im/formidable):
```js
const XLSX = require("xlsx");
const http = require("http");
const formidable = require("formidable");
const server = http.createServer((req, res) => {
const form = new formidable.IncomingForm();
form.parse(req, (err, fields, files) => {
/* grab the first file */
const f = Object.entries(files)[0][1];
const path = f.filepath;
const workbook = XLSX.readFile(path);
/* DO SOMETHING WITH workbook HERE */
});
}).listen(process.env.PORT || 7262);
```
The [`server` demo](demos/server) has more advanced examples.
</details>
<details>
<summary><b>Download files in a NodeJS process</b> (click to show)</summary>
Node 17.5 and 18.0 have native support for fetch:
```js
const XLSX = require("xlsx");
const data = await (await fetch(url)).arrayBuffer();
/* data is an ArrayBuffer */
const workbook = XLSX.read(data);
```
For broader compatibility, third-party modules are recommended.
[`request`](https://npm.im/request) requires a `null` encoding to yield Buffers:
```js
var XLSX = require("xlsx");
var request = require("request");
request({url: url, encoding: null}, function(err, resp, body) {
var workbook = XLSX.read(body);
/* DO SOMETHING WITH workbook HERE */
});
```
[`axios`](https://npm.im/axios) works the same way in browser and in NodeJS:
```js
const XLSX = require("xlsx");
const axios = require("axios");
(async() => {
const res = await axios.get(url, {responseType: "arraybuffer"});
/* res.data is a Buffer */
const workbook = XLSX.read(res.data);
/* DO SOMETHING WITH workbook HERE */
})();
```
</details>
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<details>
<summary><b>Download files in an Electron app</b> (click to show)</summary>
The `net` module in the main process can make HTTP/HTTPS requests to external
resources. Responses should be manually concatenated using `Buffer.concat`:
```js
const XLSX = require("xlsx");
const { net } = require("electron");
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const req = net.request(url);
req.on("response", (res) => {
const bufs = []; // this array will collect all of the buffers
res.on("data", (chunk) => { bufs.push(chunk); });
res.on("end", () => {
const workbook = XLSX.read(Buffer.concat(bufs));
/* DO SOMETHING WITH workbook HERE */
});
});
req.end();
```
</details>
<details>
<summary><b>Readable Streams in NodeJS</b> (click to show)</summary>
When dealing with Readable Streams, the easiest approach is to buffer the stream
and process the whole thing at the end:
```js
var fs = require("fs");
var XLSX = require("xlsx");
function process_RS(stream, cb) {
var buffers = [];
stream.on("data", function(data) { buffers.push(data); });
stream.on("end", function() {
var buffer = Buffer.concat(buffers);
var workbook = XLSX.read(buffer, {type:"buffer"});
/* DO SOMETHING WITH workbook IN THE CALLBACK */
cb(workbook);
});
}
```
</details>
<details>
<summary><b>ReadableStream in the browser</b> (click to show)</summary>
When dealing with `ReadableStream`, the easiest approach is to buffer the stream
and process the whole thing at the end:
```js
// XLSX is a global from the standalone script
async function process_RS(stream) {
/* collect data */
const buffers = [];
const reader = stream.getReader();
for(;;) {
const res = await reader.read();
if(res.value) buffers.push(res.value);
if(res.done) break;
}
/* concat */
const out = new Uint8Array(buffers.reduce((acc, v) => acc + v.length, 0));
let off = 0;
for(const u8 of arr) {
out.set(u8, off);
off += u8.length;
}
return out;
}
const data = await process_RS(stream);
/* data is Uint8Array */
const workbook = XLSX.read(data);
```
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</details>
More detailed examples are covered in the [included demos](demos/)