JS variable assigned a value is always undefined in Microsoft Edge, but not in Google Chrome

[datvm]

Please see this question here on Microsoft Learn where it's confirmed it is apparently a bug in Microsoft Edge.

I am encountering an issue where a variable is assigned a value, but the value is always undefined in Microsoft Edge. Strangely, the same code works as expected in Google Chrome. I have confirmed the assigned value is not undefined, and checked that the code does not have any way to assign undefined to the variable. Even though hovering over the variable in DevTools shows the correct value, evaluating the variable in the console still results in undefined. Here is the relevant code:

customElements.define("popup-page", class extends HTMLElement {
    // ...
    #lastDownload = 0;
    // ...

    async #download() {
        // ...
        this.#lastDownload = 0;
        // ...

            for (let i = 0; i < urls.length; i++) {
                // ...
                const id = el.downloadId = await this.#attemptItemAsync(url, maxCon, addDelay);
            }
    }

async #attemptItemAsync(url, maxCon, addDelay) {
        try {
            if (addDelay > 0) {
                const now = Date.now();
                if (now - this.#lastDownload < addDelay) {
                    await sleepAsync(now - this.#lastDownload);
                }
                this.#lastDownload = now;
            }
            
            // ...
        }
        catch {
            return;
        }
    }
});

I believe this is a bug in Microsoft Edge. When I sideloaded the same extension into Google Chrome, the bug did not occur. Please let me know if you need more information.

[captainbrosset]

Thank you for reporting this here. I have two questions:

1. Does the bug only appear in the DevTools Console? That is: the value appears as undefined in the Console, but the code works.
2. Are you able to provide a full code snippet for us to try and reproduce this locally? Right now, the code is incomplete and I can't really run it locally without inventing other parts of the code, which might not be the right ones to reproduce the issue.

Thank you.

[datvm]

@captainbrosset Hi,

1. No, the DevTool tooltip is the only place where the should-be value shows up. However, the "real" value is still undefined, making my if statement's expression false when it should be true. That is, the code doesn't perform as it should.

2. I sent it to the person at this post privately because it's a private project. Unfortunately I am not sure what causes it and cannot make a minimal reproducible example. If you provide a private channel I will send over the file.

[captainbrosset]

@datvm if you can, please send the file over as a private message either on my twitter or mastodon account, which are linked to from my github account page: https://github.com/captainbrosset/
Or send it as an email: patrickbrosset at gmail dot com.

[datvm]

@captainbrosset thanks, sent you an email.