puppeteer/docs/api/puppeteer.page.exposefunction.md

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Page.exposeFunction

Page.exposeFunction() method

The method adds a function called name on the page's window object. When called, the function executes puppeteerFunction in node.js and returns a Promise which resolves to the return value of puppeteerFunction.

If the puppeteerFunction returns a Promise, it will be awaited.

NOTE: Functions installed via page.exposeFunction survive navigations.

Signature:

class Page {exposeFunction(name: string, pptrFunction: Function | {
        default: Function;
    }): Promise<void>;}

Parameters

Parameter	Type	Description
name	string	Name of the function on the window object
pptrFunction	Function | { default: Function; }	Callback function which will be called in Puppeteer's context.

Returns:

Promise<void>

Example

An example of adding an md5 function into the page:

const puppeteer = require('puppeteer');
const crypto = require('crypto');

(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
page.on('console', (msg) => console.log(msg.text()));
await page.exposeFunction('md5', (text) =>
crypto.createHash('md5').update(text).digest('hex')
);
await page.evaluate(async () => {
// use window.md5 to compute hashes
const myString = 'PUPPETEER';
const myHash = await window.md5(myString);
console.log(`md5 of ${myString} is ${myHash}`);
});
await browser.close();
})();

An example of adding a window.readfile function into the page:

const puppeteer = require('puppeteer');
const fs = require('fs');

(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
page.on('console', (msg) => console.log(msg.text()));
await page.exposeFunction('readfile', async (filePath) => {
return new Promise((resolve, reject) => {
fs.readFile(filePath, 'utf8', (err, text) => {
   if (err) reject(err);
   else resolve(text);
 });
});
});
await page.evaluate(async () => {
// use window.readfile to read contents of a file
const content = await window.readfile('/etc/hosts');
console.log(content);
});
await browser.close();
})();