I’m working on a reporting engine right now, and one of the requirements I have is to be able to export reports as PDF files, and send PDF reports via email. We also have a management page where you can see all the dashboards, and we’d like to render a PNG thumbnail of the dashboard to show here. Our back-end is all Node.js based, and you’re probably aware that Node is not known for it’s graphics prowess. All of our reports are currently being generated by a React app, written with Gatsby.js, so what we’d like to do is load up a report in a headless browser of some sort, and then either “print” that to PDF or take a PNG image. We’re going to look at doing exactly this using Playwright and Browserless.

The basic idea here is we want an API endpoint we can call into as an authenticated user, and get it to render a PDF of a web page for us. To do this we’re going to use two tools. The first is playwright, which is a library from Microsoft for controlling a headless Chrome or Firefox browser. The second is browserless, a microservice which hosts one or more headless Chrome browsers for us.

If you have a very simple use case, you might actually be able to do this entirely with browserless with their APIs. There’s a /pdf REST API which would do pretty much what we want here. We can pass in cookies and custom headers to authenticate our user to the reporting backend, we can set the width of the viewport to something reasonable (since of course our analytics page is responsive, and we want the desktop version in our PDF reports, not the mobile version).

But, playwright offers us two nice features that make it desirable here. First it has a much more expressive API. It’s easy, for example, to load a page, wait for a certain selector to be present (or not be present) to signal that the page is loaded, and then generate a PDF or screenshot. Second, when you npm install playwright, it will download a copy of Chrome and Firefox automatically, so when we’re running this locally in development mode we don’t even need the browserless container running.

#node #web-development #developer #pdf