83 lines
2.3 KiB
Markdown
83 lines
2.3 KiB
Markdown
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<!-- Do not edit this file. It is automatically generated by API Documenter. -->
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[Home](./index.md) > [puppeteer](./puppeteer.md) > [Page](./puppeteer.page.md) > [exposeFunction](./puppeteer.page.exposefunction.md)
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## Page.exposeFunction() method
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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`.
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If the puppeteerFunction returns a `Promise`, it will be awaited.
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NOTE: Functions installed via `page.exposeFunction` survive navigations.
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<b>Signature:</b>
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```typescript
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exposeFunction(name: string, puppeteerFunction: Function): Promise<void>;
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```
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## Parameters
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| Parameter | Type | Description |
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| --- | --- | --- |
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| name | string | Name of the function on the window object |
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| puppeteerFunction | Function | Callback function which will be called in Puppeteer's context. |
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<b>Returns:</b>
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Promise<void>
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## Example
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An example of adding an `md5` function into the page:
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```js
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const puppeteer = require('puppeteer');
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const crypto = require('crypto');
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(async () => {
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const browser = await puppeteer.launch();
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const page = await browser.newPage();
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page.on('console', (msg) => console.log(msg.text()));
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await page.exposeFunction('md5', (text) =>
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crypto.createHash('md5').update(text).digest('hex')
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);
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await page.evaluate(async () => {
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// use window.md5 to compute hashes
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const myString = 'PUPPETEER';
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const myHash = await window.md5(myString);
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console.log(`md5 of ${myString} is ${myHash}`);
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});
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await browser.close();
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})();
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```
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An example of adding a `window.readfile` function into the page:
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```js
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const puppeteer = require('puppeteer');
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const fs = require('fs');
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(async () => {
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const browser = await puppeteer.launch();
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const page = await browser.newPage();
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page.on('console', (msg) => console.log(msg.text()));
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await page.exposeFunction('readfile', async (filePath) => {
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return new Promise((resolve, reject) => {
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fs.readFile(filePath, 'utf8', (err, text) => {
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if (err) reject(err);
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else resolve(text);
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});
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});
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});
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await page.evaluate(async () => {
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// use window.readfile to read contents of a file
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const content = await window.readfile('/etc/hosts');
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console.log(content);
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});
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await browser.close();
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})();
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```
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