Crawl a SPA (Single-Page Application) and generate pre In order to benefit from it, we should evaluate this API within the page context: Notice that if evaluate receives a function which returns a non-serializable value - then evaluate returns eventually undefined. To clarify - possible reasons could be that the page is loaded slowly, part of the page is lazy-loaded, or perhaps it’s navigated immediately to another page. If you want to type some text inside an input, use the page.type method: And if you want to click something, use the page.click method: After you perform an action, you can wait for a selector to appear before you proceed any further. This is a list with the available devices.

Furthermore, we adjust the viewport size according to the display points that appear here.

Note: Of course, chrome-launcher is only to demonstrate an instance creation. We introduced today the Puppeteer’s API through concrete examples. Taking screenshots through Puppeteer is a quite easy mission. This is the reason why Puppeteer’s ecosystem provides methods to launch a new Chromium instance and connect an existing instance also. Because of that, if you want to use an outside variable (a selector, for example) inside the function, you have to pass that variable as an argument to evaluate: By the way, you can’t pass an external library (get-urls, for example) as an argument. However, a few moments later, the page is really navigated to the website’s index page and rendered with a title. Capturing an area within the page. The connect method attaches the instance we just created to Puppeteer. Having the accessibility tree means we can analyze and test the accessibility support in the page. Chromium Tracing is a profiling tool that allows recording what the browser is really doing under the hood - with an emphasis on every thread, tab, and process.

For example, let’s record the browser activities during navigation: When the recording is stopped, a file called trace.json is created and contains the output that looks like: Now that we’ve the trace file, we can open it using Chrome DevTools, chrome://tracing or Timeline Viewer.

The cool thing is that we can headless almost everything in Puppeteer. Although there are projects that claim to support the variety browsers - the official team has started to maintain an experimental project that interacts with Firefox, specifically: Update: puppeteer-firefox was an experimental package to examine communication with an outdated Firefox fork, however, this project is no longer maintained.

Thereafter, we define calculateUsedBytes which goes through a collected coverage data and calculates how many bytes are being used (based on the coverage). As far as the runtime metrics, unlike load time, Puppeteer provides a neat API: We invoke the metrics method and get the following result: The interesting metric above is apparently JSHeapUsedSize which represents, in other words, the actual memory usage of the page.

Afterward, we just take the title of Page’s main frame, print it, and expect to get that as an output: puppeteer自体が他のライブラリを使っています。 依存ライブラリーのインストール package.jsonと同じ階層で npm i --save puppeteer プログラムの実行 examplesディレクトリで NODE_PATH=../ node examples/search.js Load 2 or more pages side-by-side to visually see the difference in page load.

Optional desktop viewport and throttling settings. Let’s start with a recommended structure for your project.

it’s all about placing the breakpoints right before Puppeteer’s operation.

Disclaimer: This article doesn’t claim to replace the official documentation but rather elaborate it - you definitely should go over it in order to be aligned with the most updated API specification. The next step is simply clicking on the link by the respective coordinates: Instead of changing the position explicitly, we just use click - which basically triggers mousemove, mousedown and mouseup events, one after another.
The code coverage feature was introduced officially as part of Chrome v59 - and provides the ability to measure how much code is being used, compared to the code that is actually loaded. Puppeteer is a project from the Google Chrome team which enables us to control a Chrome (or any other Chrome DevTools Protocol based browser) and execute common actions, much like in a real browser - programmatically, through a decent API. Although it’s hard to see, the second link is hovered as we planned. You can do that with the page.waitForSelector method: Handle events emitted by the Page with the page.on or page.once methods: Use on to handle every event and once to handle only the first.

Write your code inside an async IIFE in the index.js: Or create a new file that you will import: Also, a nodemon script can be useful here to re-run your code after you make changes: You can emulate a device with page.emulate. Puppeteer allows taking screenshots of the page and generating PDFs from the content, easily. Adding them programmatically is possible either, simply by inserting the debugger; statement, obviously. Note: All explanations about the different timings above are available here. Check it out during the article or afterwards. Puppeteer Sharp - Examples Puppeteer Sharp is a .NET port of the official Node.JS Puppeteer API. Moreover, it’s also possible to control the type, quality and even clipping the image: Here’s the output:

Apparently - some of you may wonder if it’s possible to sleep the browser with a specified time period, so: The first approach is merely a function that resolves a promise when setTimeout finishes. .

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When writing code, we should be aware of what kinds of ways are available to debug our program. Let’s type some text within the search input: Notice that we wait for the toolbar (instead of the API sidebar). Active Reliability for Modern DevOps Teams. All we do, is instructing Puppeteer to wait until the page renders a title meta element, which is achieved by invoking waitForSelector. In case you wonder - headless mode is mostly useful for environments that don’t really need the UI or neither support such an interface. Well, if you wish to get some useful code snippets of Puppeteer API for Visual Studio Code - then the following extension might interest you: You’re welcome to take a look at the extension page. Note: We can obtain the full tree through setting interestingOnly to false.

Presently, the way to go is by setting the PUPPETEER_PRODUCT environment variable to firefox and so fetching the binary of Firefox Nightly. The second approach, however, is much simpler but demands having a page instance (we’ll get to that later). An overview, concrete guide and kinda cheat sheet for the popular browser automation library, based on Node.js, which provides a high-level API over the Chrome DevTools Protocol. On top of typing text, it’s obviously possible to trigger keyboard events: Basically, we press ArrowDown twice and Enter in order to choose the third search result. Notice it’s created on the default browser context. It’s easy to understand that setUserAgent defines a specific user agent for the page, whereas setViewport modifies the viewport definition of the page. Similar to the mouse, Puppeteer represents the keyboard by a class called Keyboard - and every Page instance holds such an instance.

The Page class supports emitting of various events by actually extending the Node.js’s EventEmitter object. In case we want to debug the application itself in the opened browser - it basically means to open the DevTools and start debugging as usual: Notice that we use devtools which launches the browser in a headful mode by default and opens the DevTools automatically.

If nothing happens, download GitHub Desktop and try again. Puppeteer allows analyzing and testing the accessibility support in the page.

You then listen for the request event, and you call request.abort(), request.continue(), or request.respond(): Reveal animations on scroll with react-spring, Extremely fast loading with Gatsby and self-hosted fonts.

On top of that, we utilize waitForTarget in order to hold the browser process until we terminate it explicitly.

Naturally, it should have a Chromium instance to interact with. As we know, Puppeteer is executed in a Node.js process - which is absolutely separated from the browser process. Notice that the result is actually the output of Performance.getMetrics, which is part of Chrome DevTools Protocol. Puppeteer is either useful for generating a PDF file from the page content. Importing a trace file. Puppeteer allows speeding up the page performance by providing information about the dead code, handy metrics and manually tracing ability.

Notice this method is asynchronous (like most Puppeteer’s methods) which, as we know, returns a Promise. When navigating to Puppeteer’s website, the title element is evaluated as an empty string. Here are a few examples to get you started: Generate screenshots and PDFs of pages.

Use case-driven examples for using Puppeteer and headless chrome. That’s fairly probable we would like to see how our script instructs the browser and what’s actually displayed, at some point.

The easiest way to interact with the browser is by launching a Chromium instance using Puppeteer: The launch method initializes the instance at first, and then attaching Puppeteer to that. Then, we simply fetch the webSocketDebuggerUrl value of the created instance.
Puppeteer’s library provides tools for approximating how the page looks and behaves on various devices, which are pretty useful when testing a website’s responsiveness.

The browser context allows separating different sessions for a single browser instance. Once we’ve the binary, we merely need to change the product to “firefox” whereas the rest of the lines remain the same - what means we’re already familiar with how to launch the browser: ⚠️ Pay attention - the API integration isn’t totally ready yet and implemented progressively.

From looking at the list above - we clearly understand that the supported events include aspects of loading, frames, metrics, console, errors, requests, responses and even more!

That’s exactly why we stringify window.performance when evaluating within the page context.

On top of that, it provides a method called emulate which is practically a shortcut for invoking setUserAgent and setViewport, one after another.

Let’s start with a recommended . GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together. Verify all the resources you expect are being cached by a service worker for offline.

Furthermore, this tracing ability is possible with Puppeteer either - which, as we might guess, practically uses the Chrome DevTools Protocol.

In case of multiple pages, each one has its own user agent and viewport definition. Determine if your lazy loaded images will be seen correctly by Google Search. A default browser context is created as soon as creating a browser instance, but we can create additional browser contexts as necessary: Apart from the fact that we demonstrate how to access each context, we need to know that the only way to terminate the default context is by closing the browser instance - which, in fact, terminates all the contexts that belong to the browser.