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fix: much better TypeScript definitions #6837

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fix: much better TypeScript definitions #6837

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122 changes: 66 additions & 56 deletions README.md
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@@ -1,7 +1,9 @@
# Puppeteer

<!-- [START badges] -->

[![Build status](https://github.com/puppeteer/puppeteer/workflows/run-checks/badge.svg)](https://github.com/puppeteer/puppeteer/actions?query=workflow%3Arun-checks) [![npm puppeteer package](https://img.shields.io/npm/v/puppeteer.svg)](https://npmjs.org/package/puppeteer)

<!-- [END badges] -->

<img src="https://user-images.githubusercontent.com/10379601/29446482-04f7036a-841f-11e7-9872-91d1fc2ea683.png" height="200" align="right">
Expand All @@ -11,21 +13,23 @@
> Puppeteer is a Node library which provides a high-level API to control Chrome or Chromium over the [DevTools Protocol](https://chromedevtools.github.io/devtools-protocol/). Puppeteer runs [headless](https://developers.google.com/web/updates/2017/04/headless-chrome) by default, but can be configured to run full (non-headless) Chrome or Chromium.

<!-- [START usecases] -->

###### What can I do?

Most things that you can do manually in the browser can be done using Puppeteer! Here are a few examples to get you started:

* Generate screenshots and PDFs of pages.
* Crawl a SPA (Single-Page Application) and generate pre-rendered content (i.e. "SSR" (Server-Side Rendering)).
* Automate form submission, UI testing, keyboard input, etc.
* Create an up-to-date, automated testing environment. Run your tests directly in the latest version of Chrome using the latest JavaScript and browser features.
* Capture a [timeline trace](https://developers.google.com/web/tools/chrome-devtools/evaluate-performance/reference) of your site to help diagnose performance issues.
* Test Chrome Extensions.
- Generate screenshots and PDFs of pages.
- Crawl a SPA (Single-Page Application) and generate pre-rendered content (i.e. "SSR" (Server-Side Rendering)).
- Automate form submission, UI testing, keyboard input, etc.
- Create an up-to-date, automated testing environment. Run your tests directly in the latest version of Chrome using the latest JavaScript and browser features.
- Capture a [timeline trace](https://developers.google.com/web/tools/chrome-devtools/evaluate-performance/reference) of your site to help diagnose performance issues.
- Test Chrome Extensions.
<!-- [END usecases] -->

Give it a spin: https://try-puppeteer.appspot.com/

<!-- [START getstarted] -->

## Getting Started

### Installation
Expand All @@ -39,7 +43,6 @@ npm i puppeteer

Note: When you install Puppeteer, it downloads a recent version of Chromium (~170MB Mac, ~282MB Linux, ~280MB Win) that is guaranteed to work with the API. To skip the download, or to download a different browser, see [Environment variables](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#environment-variables).


### puppeteer-core

Since version 1.7.0 we publish the [`puppeteer-core`](https://www.npmjs.com/package/puppeteer-core) package,
Expand All @@ -65,7 +68,7 @@ Node 8.9.0+. Starting from v3.0.0 Puppeteer starts to rely on Node 10.18.1+. All
Puppeteer will be familiar to people using other browser testing frameworks. You create an instance
of `Browser`, open pages, and then manipulate them with [Puppeteer's API](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#).

**Example** - navigating to https://example.com and saving a screenshot as *example.png*:
**Example** - navigating to https://example.com and saving a screenshot as _example.png_:

Save file as **example.js**

Expand All @@ -76,7 +79,7 @@ const puppeteer = require('puppeteer');
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://example.com');
await page.screenshot({path: 'example.png'});
await page.screenshot({ path: 'example.png' });

await browser.close();
})();
Expand All @@ -88,7 +91,7 @@ Execute script on the command line
node example.js
```

Puppeteer sets an initial page size to 800×600px, which defines the screenshot size. The page size can be customized with [`Page.setViewport()`](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#pagesetviewportviewport).
Puppeteer sets an initial page size to 800×600px, which defines the screenshot size. The page size can be customized with [`Page.setViewport()`](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#pagesetviewportviewport).

**Example** - create a PDF.

Expand All @@ -100,8 +103,10 @@ const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://news.ycombinator.com', {waitUntil: 'networkidle2'});
await page.pdf({path: 'hn.pdf', format: 'A4'});
await page.goto('https://news.ycombinator.com', {
waitUntil: 'networkidle2',
});
await page.pdf({ path: 'hn.pdf', format: 'A4' });

await browser.close();
})();
Expand Down Expand Up @@ -132,7 +137,7 @@ const puppeteer = require('puppeteer');
return {
width: document.documentElement.clientWidth,
height: document.documentElement.clientHeight,
deviceScaleFactor: window.devicePixelRatio
deviceScaleFactor: window.devicePixelRatio,
};
});

Expand All @@ -153,14 +158,15 @@ See [`Page.evaluate()`](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/
<!-- [END getstarted] -->

<!-- [START runtimesettings] -->

## Default runtime settings

**1. Uses Headless mode**

Puppeteer launches Chromium in [headless mode](https://developers.google.com/web/updates/2017/04/headless-chrome). To launch a full version of Chromium, set the [`headless` option](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#puppeteerlaunchoptions) when launching a browser:

```js
const browser = await puppeteer.launch({headless: false}); // default is true
const browser = await puppeteer.launch({ headless: false }); // default is true
```

**2. Runs a bundled version of Chromium**
Expand All @@ -170,7 +176,7 @@ is guaranteed to work out of the box. To use Puppeteer with a different version
pass in the executable's path when creating a `Browser` instance:

```js
const browser = await puppeteer.launch({executablePath: '/path/to/Chrome'});
const browser = await puppeteer.launch({ executablePath: '/path/to/Chrome' });
```

You can also use Puppeteer with Firefox Nightly (experimental support). See [`Puppeteer.launch()`](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#puppeteerlaunchoptions) for more information.
Expand All @@ -189,39 +195,38 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
- [Examples](https://github.com/puppeteer/puppeteer/tree/main/examples/)
- [Community list of Puppeteer resources](https://github.com/transitive-bullshit/awesome-puppeteer)


<!-- [START debugging] -->

## Debugging tips

1. Turn off headless mode - sometimes it's useful to see what the browser is
displaying. Instead of launching in headless mode, launch a full version of
the browser using `headless: false`:
1. Turn off headless mode - sometimes it's useful to see what the browser is
displaying. Instead of launching in headless mode, launch a full version of
the browser using `headless: false`:

```js
const browser = await puppeteer.launch({headless: false});
const browser = await puppeteer.launch({ headless: false });
```

2. Slow it down - the `slowMo` option slows down Puppeteer operations by the
specified amount of milliseconds. It's another way to help see what's going on.
2. Slow it down - the `slowMo` option slows down Puppeteer operations by the
specified amount of milliseconds. It's another way to help see what's going on.

```js
const browser = await puppeteer.launch({
headless: false,
slowMo: 250 // slow down by 250ms
slowMo: 250, // slow down by 250ms
});
```

3. Capture console output - You can listen for the `console` event.
This is also handy when debugging code in `page.evaluate()`:
3. Capture console output - You can listen for the `console` event.
This is also handy when debugging code in `page.evaluate()`:

```js
page.on('console', msg => console.log('PAGE LOG:', msg.text()));
page.on('console', (msg) => console.log('PAGE LOG:', msg.text()));

await page.evaluate(() => console.log(`url is ${location.href}`));
```

4. Use debugger in application code browser
4. Use debugger in application code browser

There are two execution context: node.js that is running test code, and the browser
running application code being tested. This lets you debug code in the
Expand All @@ -230,26 +235,28 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
- Use `{devtools: true}` when launching Puppeteer:

```js
const browser = await puppeteer.launch({devtools: true});
const browser = await puppeteer.launch({ devtools: true });
```

- Change default test timeout:

jest: `jest.setTimeout(100000);`
jest: `jest.setTimeout(100000);`

jasmine: `jasmine.DEFAULT_TIMEOUT_INTERVAL = 100000;`
jasmine: `jasmine.DEFAULT_TIMEOUT_INTERVAL = 100000;`

mocha: `this.timeout(100000);` (don't forget to change test to use [function and not '=>'](https://stackoverflow.com/a/23492442))
mocha: `this.timeout(100000);` (don't forget to change test to use [function and not '=>'](https://stackoverflow.com/a/23492442))

- Add an evaluate statement with `debugger` inside / add `debugger` to an existing evaluate statement:
- Add an evaluate statement with `debugger` inside / add `debugger` to an existing evaluate statement:

```js
await page.evaluate(() => {debugger;});
await page.evaluate(() => {
debugger;
});
```

The test will now stop executing in the above evaluate statement, and chromium will stop in debug mode.
The test will now stop executing in the above evaluate statement, and chromium will stop in debug mode.

5. Use debugger in node.js
5. Use debugger in node.js

This will let you debug test code. For example, you can step over `await page.click()` in the node.js script and see the click happen in the application code browser.

Expand All @@ -270,37 +277,36 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
- In the newly opened test browser, type `F8` to resume test execution
- Now your `debugger` will be hit and you can debug in the test browser

6. Enable verbose logging - internal DevTools protocol traffic
will be logged via the [`debug`](https://github.com/visionmedia/debug) module under the `puppeteer` namespace.

6. Enable verbose logging - internal DevTools protocol traffic
will be logged via the [`debug`](https://github.com/visionmedia/debug) module under the `puppeteer` namespace.

# Basic verbose logging
env DEBUG="puppeteer:*" node script.js
# Basic verbose logging
env DEBUG="puppeteer:*" node script.js

# Protocol traffic can be rather noisy. This example filters out all Network domain messages
env DEBUG="puppeteer:*" env DEBUG_COLORS=true node script.js 2>&1 | grep -v '"Network'
# Protocol traffic can be rather noisy. This example filters out all Network domain messages
env DEBUG="puppeteer:*" env DEBUG_COLORS=true node script.js 2>&1 | grep -v '"Network'

7. Debug your Puppeteer (node) code easily, using [ndb](https://github.com/GoogleChromeLabs/ndb)
7. Debug your Puppeteer (node) code easily, using [ndb](https://github.com/GoogleChromeLabs/ndb)

- `npm install -g ndb` (or even better, use [npx](https://github.com/zkat/npx)!)
- `npm install -g ndb` (or even better, use [npx](https://github.com/zkat/npx)!)

- add a `debugger` to your Puppeteer (node) code
- add a `debugger` to your Puppeteer (node) code

- add `ndb` (or `npx ndb`) before your test command. For example:
- add `ndb` (or `npx ndb`) before your test command. For example:

`ndb jest` or `ndb mocha` (or `npx ndb jest` / `npx ndb mocha`)
`ndb jest` or `ndb mocha` (or `npx ndb jest` / `npx ndb mocha`)

- debug your test inside chromium like a boss!
- debug your test inside chromium like a boss!

<!-- [END debugging] -->


<!-- [START typescript] -->

## Usage with TypeScript

We have recently completed a migration to move the Puppeteer source code from JavaScript to TypeScript and we're currently working on shipping type definitions for TypeScript with Puppeteer's npm package.
We have recently completed a migration to move the Puppeteer source code from JavaScript to TypeScript and as of version 7.0.1 we ship our own built-in type definitions.

Until this work is complete we recommend installing the Puppeteer type definitions from the [DefinitelyTyped](https://definitelytyped.org/) repository:
If you are on a version older than 7, we recommend installing the Puppeteer type definitions from the [DefinitelyTyped](https://definitelytyped.org/) repository:

```bash
npm install --save-dev @types/puppeteer
Expand All @@ -310,7 +316,6 @@ The types that you'll see appearing in the Puppeteer source code are based off t

<!-- [END typescript] -->


## Contributing to Puppeteer

Check out [contributing guide](https://github.com/puppeteer/puppeteer/blob/main/CONTRIBUTING.md) to get an overview of Puppeteer development.
Expand Down Expand Up @@ -344,6 +349,7 @@ The goals of the project are:
- Learn more about the pain points of automated browser testing and help fill those gaps.

We adapt [Chromium principles](https://www.chromium.org/developers/core-principles) to help us drive product decisions:

- **Speed**: Puppeteer has almost zero performance overhead over an automated page.
- **Security**: Puppeteer operates off-process with respect to Chromium, making it safe to automate potentially malicious pages.
- **Stability**: Puppeteer should not be flaky and should not leak memory.
Expand All @@ -352,6 +358,7 @@ We adapt [Chromium principles](https://www.chromium.org/developers/core-principl
#### Q: Is Puppeteer replacing Selenium/WebDriver?

**No**. Both projects are valuable for very different reasons:

- Selenium/WebDriver focuses on cross-browser automation; its value proposition is a single standard API that works across all major browsers.
- Puppeteer focuses on Chromium; its value proposition is richer functionality and higher reliability.

Expand All @@ -367,13 +374,15 @@ That said, you **can** use Puppeteer to run tests against Chromium, e.g. using t
We see Puppeteer as an **indivisible entity** with Chromium. Each version of Puppeteer bundles a specific version of Chromium – **the only** version it is guaranteed to work with.

This is not an artificial constraint: A lot of work on Puppeteer is actually taking place in the Chromium repository. Here’s a typical story:

- A Puppeteer bug is reported: https://github.com/puppeteer/puppeteer/issues/2709
- It turned out this is an issue with the DevTools protocol, so we’re fixing it in Chromium: https://chromium-review.googlesource.com/c/chromium/src/+/1102154
- Once the upstream fix is landed, we roll updated Chromium into Puppeteer: https://github.com/puppeteer/puppeteer/pull/2769

However, oftentimes it is desirable to use Puppeteer with the official Google Chrome rather than Chromium. For this to work, you should install a `puppeteer-core` version that corresponds to the Chrome version.

For example, in order to drive Chrome 71 with puppeteer-core, use `chrome-71` npm tag:

```bash
npm install puppeteer-core@chrome-71
```
Expand All @@ -382,7 +391,6 @@ npm install puppeteer-core@chrome-71

Look for the `chromium` entry in [revisions.ts](https://github.com/puppeteer/puppeteer/blob/main/src/revisions.ts). To find the corresponding Chromium commit and version number, search for the revision prefixed by an `r` in [OmahaProxy](https://omahaproxy.appspot.com/)'s "Find Releases" section.


#### Q: Which Firefox version does Puppeteer use?

Since Firefox support is experimental, Puppeteer downloads the latest [Firefox Nightly](https://wiki.mozilla.org/Nightly) when the `PUPPETEER_PRODUCT` environment variable is set to `firefox`. That's also why the value of `firefox` in [revisions.ts](https://github.com/puppeteer/puppeteer/blob/main/src/revisions.ts) is `latest` -- Puppeteer isn't tied to a particular Firefox version.
Expand All @@ -409,6 +417,7 @@ In browsers, input events could be divided into two big groups: trusted vs. untr
- **Untrusted event**: events generated by Web APIs, e.g. `document.createEvent` or `element.click()` methods.

Websites can distinguish between these two groups:

- using an [`Event.isTrusted`](https://developer.mozilla.org/en-US/docs/Web/API/Event/isTrusted) event flag
- sniffing for accompanying events. For example, every trusted `'click'` event is preceded by `'mousedown'` and `'mouseup'` events.

Expand All @@ -424,10 +433,11 @@ await page.evaluate(() => {

You may find that Puppeteer does not behave as expected when controlling pages that incorporate audio and video. (For example, [video playback/screenshots is likely to fail](https://github.com/puppeteer/puppeteer/issues/291).) There are two reasons for this:

* Puppeteer is bundled with Chromium — not Chrome — and so by default, it inherits all of [Chromium's media-related limitations](https://www.chromium.org/audio-video). This means that Puppeteer does not support licensed formats such as AAC or H.264. (However, it is possible to force Puppeteer to use a separately-installed version Chrome instead of Chromium via the [`executablePath` option to `puppeteer.launch`](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#puppeteerlaunchoptions). You should only use this configuration if you need an official release of Chrome that supports these media formats.)
* Since Puppeteer (in all configurations) controls a desktop version of Chromium/Chrome, features that are only supported by the mobile version of Chrome are not supported. This means that Puppeteer [does not support HTTP Live Streaming (HLS)](https://caniuse.com/#feat=http-live-streaming).
- Puppeteer is bundled with Chromium — not Chrome — and so by default, it inherits all of [Chromium's media-related limitations](https://www.chromium.org/audio-video). This means that Puppeteer does not support licensed formats such as AAC or H.264. (However, it is possible to force Puppeteer to use a separately-installed version Chrome instead of Chromium via the [`executablePath` option to `puppeteer.launch`](https://github.com/puppeteer/puppeteer/blob/v7.0.1/docs/api.md#puppeteerlaunchoptions). You should only use this configuration if you need an official release of Chrome that supports these media formats.)
- Since Puppeteer (in all configurations) controls a desktop version of Chromium/Chrome, features that are only supported by the mobile version of Chrome are not supported. This means that Puppeteer [does not support HTTP Live Streaming (HLS)](https://caniuse.com/#feat=http-live-streaming).

#### Q: I am having trouble installing / running Puppeteer in my test environment. Where should I look for help?

We have a [troubleshooting](https://github.com/puppeteer/puppeteer/blob/main/docs/troubleshooting.md) guide for various operating systems that lists the required dependencies.

#### Q: How do I try/test a prerelease version of Puppeteer?
Expand All @@ -443,11 +453,11 @@ Please note that prerelease may be unstable and contain bugs.
#### Q: I have more questions! Where do I ask?

There are many ways to get help on Puppeteer:

- [bugtracker](https://github.com/puppeteer/puppeteer/issues)
- [Stack Overflow](https://stackoverflow.com/questions/tagged/puppeteer)
- [slack channel](https://join.slack.com/t/puppeteer/shared_invite/enQtMzU4MjIyMDA5NTM4LWI0YTE0MjM0NWQzYmE2MTRmNjM1ZTBkN2MxNmJmNTIwNTJjMmFhOWFjMGExMDViYjk2YjU2ZmYzMmE1NmExYzc)

Make sure to search these channels before posting your question.


<!-- [END faq] -->