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Version: 22.12.0

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 {
abstract 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 1

An example of adding an md5 function into the page:

import puppeteer from 'puppeteer';
import crypto from '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();
})();

Example 2

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

import puppeteer from 'puppeteer';
import fs from '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();
})();