`mjml2html` render in web worker throws `Uncaught ReferenceError: window is not defined`

[jlarmstrongiv]

Describe the bug

In a web worker:

mjml-browser.js?v=275a58ae:25 Uncaught ReferenceError: window is not defined
    at ../../../node_modules/mjml-browser/lib/index.js (mjml-browser.js?v=275a58ae:25:7)
    at __require2 (chunk-IRSSH5FH.js?v=275a58ae:23:50)
    at mjml-browser.js?v=275a58ae:24126:16

To Reproduce
Steps to reproduce the behavior:

1. In vite, create a web worker
2. Try importing import mjml2html from "mjml-browser";
3. See error

Expected behavior
I expect mjml-browser to work in web workers, without throwing any errors. It’s a cpu heavy process that would be perfect for web workers

MJML environment (please complete the following information):

• OS: MacOS
• MJML Version: 4.15.3
• MJML tool used: mjml-browser

Email sending environment(for rendering issues):
N/A

Affected email clients (for rendering issues):
N/A

Screenshots
N/A

Additional context
window is not a global variable in web workers https://stackoverflow.com/a/11237259

[bmcminn]

As you mentioned window is not available to web worker contexts.
https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Functions_and_classes_available_to_workers

The way the mjml-browser build script works, it just dumps out a generic amd style export that binds the window object.
build script source: https://github.com/mjmlio/mjml/blob/master/packages/mjml-browser/webpack.config.js
public compiled source: https://cdn.jsdelivr.net/npm/mjml-browser@4.15.3/lib/index.js

This would likely require a mjml-webworker package to be built for this use case.

[jlarmstrongiv]

If we remove the window binding (which the mjml library does not depend on), then the mjml-browser package would work in web workers.

So, I’m not sure if a separate package is required, as long as we modify the generic amd style export in some way:

• bind to globalThis instead of window
• only bind to window if it exists

[crummy]

I think that would fix Deno as well, which reports (as of Deno v2):

Uncaught (in promise) ReferenceError: window is not defined
    at https://esm.sh/v135/mjml-browser@4.14.1/denonext/mjml-browser.mjs:2:894
    at https://esm.sh/v135/mjml-browser@4.14.1/denonext/mjml-browser.mjs:2:213
    at https://esm.sh/v135/mjml-browser@4.14.1/denonext/mjml-browser.mjs:942:2375

    info: window global is not available in Deno 2.
    hint: Replace `window` with `globalThis`.

[iRyusa]

I'lll see what I can do when I'll finish #2908

[iRyusa]

Can you test with 5.x branch ? I wonder if you'll need prettier-standalone instead of prettier too

[greg6775]

Adding import "data:text/javascript,globalThis.window = globalThis;"; as a temporary fallback should work, until we get a fixed version.

[jlarmstrongiv]

Be sure to delete that window assignment after importing mjml-browser, otherwise you’ll likely break other libraries