Hey @nguyentrananhkhoa81, thanks for posting. Would you be able to provide any additional information to the specific issue you’re running into with regards to the integration? I can say that if it has to do with an issue with your sign up form, Klaviyo does not offer support for any version of Internet Explorer when it comes to sign up forms. Built-in signup forms will not render for browsers using Internet Explorer. Legacy signup forms will continue to render for those using any type of web browser.

If this does happen to be the case, the legacy form is the best way to ensure that someone using an out of date browser is able to see the form. Here is a link that provides information on How to Add Legacy Sign Up Forms.

If the issue does not have to do with the sign up form, feel free to add additional background.

Hi @Paul S , thanks for answer my question. The error is logged on console just right after the my site is loaded, before I touched anything on my web.

So to provide some additional context here:

Klaviyo does not and historically has never supported IE. Because of that, the errors that you are seeing based on the screenshot that was provided is an expected behavior.

As of this precise moment in time the error will continue to log but this could change in the future, however, at this point in time this will be a persistent issue for IE. 

I found that klaviyo try to load other script including the vendors~signupForm.js. I guess that the arrow function in those script cause my problem. Is there any solution for it?
FYI, I‘m using angular 9 with SSR. Browser: IE11.

https://caniuse.com/arrow-functions.