`instanceof` Fails in Playwright Because Class Info Is Lost
I have an application where I'm using Web Components. In one specific area, I'm running a test to make sure that the element which I'm working with is the correct type. I do this by running
if (element instanceof MyCustomElement) {
// ...
}This works perfectly fine with vite. But when I run the Playwright tests, this logic fails because the instanceof test fails. Apparently, Playwright (or something else) is transforming class MyCustomElement extends HTMLElement { } into function HTMLElement { (native code) }, and this seems to be the reason for the failure.
Any ideas on what's causing this? And ideas on how to just work with the class? I don't want my JS getting transpiled.
This thread is trying to answer question "Why does the `instanceof` test fail in Playwright when used with Web Components and how can it be resolved?"
The issue was that the custom element was not upgraded by the time I did the check. So I had to manually call customElements.upgrade to get the job done. This is resolved now, though it's unrelated to playwright.
See: https://developer.mozilla.org/en-US/docs/Web/API/CustomElementRegistry/upgrade
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