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| title |
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| Headless Automation |
import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem';
Headless automation involves controlling "headless browsers" to access websites and submit or download data. It is also possible to automate browsers using custom browser extensions.
The SheetJS standalone script can be added to
any website by inserting a SCRIPT tag. Headless browsers usually provide
utility functions for running custom snippets in the browser and passing data
back to the automation script.
Use Case
This demo focuses on exporting table data to a workbook. Headless browsers do not generally support passing objects between the browser context and the automation script, so the file data must be generated in the browser context and sent back to the automation script for saving in the file system. Steps:
-
Launch the headless browser and load the target site.
-
Add the standalone SheetJS build to the page in a
SCRIPTtag. -
Add a script to the page (in the browser context) that will:
- Make a workbook object from the first table using
XLSX.utils.table_to_book - Generate the bytes for an XLSB file using
XLSX.write - Send the bytes back to the automation script
- When the automation context receives data, save to a file
This demo exports data from https://sheetjs.com/demos/table.
:::note
It is also possible to parse files from the browser context, but parsing from the automation context is more efficient and strongly recommended.
:::
Puppeteer
Puppeteer enables headless Chromium automation for NodeJS. Releases ship with an installer script. Installation is straightforward:
npm i https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz puppeteer
Binary strings are the favored data type. They can be safely passed from the
browser context to the automation script. NodeJS provides an API to write
binary strings to file (fs.writeFileSync using encoding binary).
To run the example, after installing the packages, save the following script to
SheetJSPuppeteer.js and run node SheetJSPuppeteer.js. Steps are commented:
const fs = require("fs");
const puppeteer = require('puppeteer');
(async () => {
/* (1) Load the target page */
const browser = await puppeteer.launch();
const page = await browser.newPage();
page.on("console", msg => console.log("PAGE LOG:", msg.text()));
await page.setViewport({width: 1920, height: 1080});
await page.goto('https://sheetjs.com/demos/table');
/* (2) Load the standalone SheetJS build from the CDN */
await page.addScriptTag({ url: 'https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js' });
/* (3) Run the snippet in browser and return data */
const bin = await page.evaluate(() => {
/* NOTE: this function will be evaluated in the browser context.
`page`, `fs` and `puppeteer` are not available.
`XLSX` will be available thanks to step 2 */
/* find first table */
var table = document.body.getElementsByTagName('table')[0];
/* call table_to_book on first table */
var wb = XLSX.utils.table_to_book(table);
/* generate XLSB and return binary string */
return XLSX.write(wb, {type: "binary", bookType: "xlsb"});
});
/* (4) write data to file */
fs.writeFileSync("SheetJSPuppeteer.xlsb", bin, { encoding: "binary" });
await browser.close();
})();
This script will generate SheetJSPuppeteer.xlsb which can be opened in Excel.
:::caution
Deno Puppeteer is a fork. It is not officially supported by the Puppeteer team.
:::
Installation is straightforward:
env PUPPETEER_PRODUCT=chrome deno run -A --unstable https://deno.land/x/puppeteer@14.1.1/install.ts
Base64 strings are the favored data type. They can be safely passed from the
browser context to the automation script. Deno can decode the Base64 strings
and write the decoded Uint8Array data to file with Deno.writeFileSync
To run the example, after installing the packages, save the following script to
SheetJSPuppeteer.ts and run deno run -A --unstable SheetJSPuppeteer.js.
import puppeteer from "https://deno.land/x/puppeteer@14.1.1/mod.ts";
import { decode } from "https://deno.land/std/encoding/base64.ts"
/* (1) Load the target page */
const browser = await puppeteer.launch();
const page = await browser.newPage();
page.on("console", msg => console.log("PAGE LOG:", msg.text()));
await page.setViewport({width: 1920, height: 1080});
await page.goto('https://sheetjs.com/demos/table');
/* (2) Load the standalone SheetJS build from the CDN */
await page.addScriptTag({ url: 'https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js' });
/* (3) Run the snippet in browser and return data */
const b64 = await page.evaluate(() => {
/* NOTE: this function will be evaluated in the browser context.
`page`, `fs` and `puppeteer` are not available.
`XLSX` will be available thanks to step 2 */
/* find first table */
var table = document.body.getElementsByTagName('table')[0];
/* call table_to_book on first table */
var wb = XLSX.utils.table_to_book(table);
/* generate XLSB and return binary string */
return XLSX.write(wb, {type: "base64", bookType: "xlsb"});
});
/* (4) write data to file */
Deno.writeFileSync("SheetJSPuppeteer.xlsb", decode(b64));
await browser.close();
This script will generate SheetJSPuppeteer.xlsb which can be opened in Excel.
Playwright
Playwright presents a unified scripting framework for Chromium, WebKit, and other browsers. It draws inspiration from Puppeteer. In fact, the example code is almost identical!
npm i https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz playwright
To run the example, after installing the packages, save the following script to
SheetJSPlaywright.js and run node SheetJSPlaywright.js. Import divergences
from the Puppeteer example are highlighted below:
const fs = require("fs");
// highlight-next-line
const { webkit } = require('playwright'); // import desired browser
(async () => {
/* (1) Load the target page */
// highlight-next-line
const browser = await webkit.launch(); // launch desired browser
const page = await browser.newPage();
page.on("console", msg => console.log("PAGE LOG:", msg.text()));
// highlight-next-line
await page.setViewportSize({width: 1920, height: 1080}); // different name :(
await page.goto('https://sheetjs.com/demos/table');
/* (2) Load the standalone SheetJS build from the CDN */
await page.addScriptTag({ url: 'https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js' });
/* (3) Run the snippet in browser and return data */
const bin = await page.evaluate(() => {
/* NOTE: this function will be evaluated in the browser context.
`page`, `fs` and the browser engine are not available.
`XLSX` will be available thanks to step 2 */
/* find first table */
var table = document.body.getElementsByTagName('table')[0];
/* call table_to_book on first table */
var wb = XLSX.utils.table_to_book(table);
/* generate XLSB and return binary string */
return XLSX.write(wb, {type: "binary", bookType: "xlsb"});
});
/* (4) write data to file */
fs.writeFileSync("SheetJSPlaywright.xlsb", bin, { encoding: "binary" });
await browser.close();
})();
PhantomJS
PhantomJS is a headless web browser powered by WebKit.
:::warning
This information is provided for legacy deployments. PhantomJS development has been suspended and there are known vulnerabilities, so new projects should use alternatives. For WebKit automation, new projects should use Playwright.
:::
Binary strings are the favored data type. They can be safely passed from the
browser context to the automation script. PhantomJS provides an API to write
binary strings to file (fs.write using mode wb).
To run the example, save the following script to SheetJSPhantom.js in the same
folder as phantomjs.exe or phantomjs and run
./phantomjs SheetJSPhantom.js ## MacOS / Linux
.\phantomjs.exe SheetJSPhantom.js ## windows
The steps are marked in the comments:
var page = require('webpage').create();
page.onConsoleMessage = function(msg) { console.log(msg); };
/* (1) Load the target page */
page.open('https://sheetjs.com/demos/table', function() {
/* (2) Load the standalone SheetJS build from the CDN */
page.includeJs("https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js", function() {
/* (3) Run the snippet in browser and return data */
var bin = page.evaluateJavaScript([ "function(){",
/* find first table */
"var table = document.body.getElementsByTagName('table')[0];",
/* call table_to_book on first table */
"var wb = XLSX.utils.table_to_book(table);",
/* generate XLSB file and return binary string */
"return XLSX.write(wb, {type: 'binary', bookType: 'xlsb'});",
"}" ].join(""));
/* (4) write data to file */
require("fs").write("SheetJSPhantomJS.xlsb", bin, "wb");
phantom.exit();
});
});
:::caution
PhantomJS is very finicky and will hang if there are script errors. It is strongly recommended to add verbose logging and to lint scripts before use.
:::