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TypeError: Right-hand side of 'instanceof' is not an object

See original GitHub issue

🐞 bug report

Affected Package

The issue is caused by package @angular/zone.js

Is this a regression?

Yes, the previous version in which this bug was not present was: ....

Description

instanceof is not safe operation, so if you monkeypatch such substantial method as Object.prototype.toString, you have to use try…catch

🔬 Minimal Reproduction

https://stackblitz.com/...

🔥 Exception or Error

TypeError: Right-hand side of 'instanceof' is not an object

🌍 Your Environment

Angular Version:

Anything else relevant?

Issue Analytics

State:
Created 3 years ago
Comments:7 (6 by maintainers)

Top GitHub Comments

1reaction

JiaLiPassioncommented, Aug 10, 2020

@rifler, I can reproduce the issue.

<html>
  <body>
    <script src="./node_modules/zone.js/dist/zone.js"></script>
    <script>
      window[Zone.__symbol__('ZoneAwarePromise')] = undefined;
      window[Zone.__symbol__('Promise')] = undefined;
      const obj = {};

      console.log('toString', obj.toString());
    </script>
  </body>
</html>

And about the fix, use try/catch will impact the performance and also swallow the error. So the recommend fix is

        Object.prototype.toString = function () {
            if (typeof Promise !== 'undefined' && this instanceof Promise) {
                return PROMISE_OBJECT_TO_STRING;
            }
            return originalObjectToString.call(this);
        };

could you update the PR? thanks!

1reaction

AndrewKushnircommented, Aug 10, 2020

Hi @rifler, thanks for providing additional information.

I’m adding @JiaLiPassion to this thread to get his opinion from the ZoneJS standpoint (he should also have an access to reopen PR #38350 once the root cause is identified).

Thank you.

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