Easiest way to alert users in IE that the page is not supported in IE

I'm looking for the easiest way to tell users on any version of IE that the webpage does not work in IE. A simple alert will do.

Stack

Vue 2, Nuxt 2

Issue

IE can't interpret ES6, so an alert in mounted or any method for that matter, does not work.

I read somewhere that writing:

mounted: function () {}

Instead of:

mounted() {}

Should do the trick, but it does not.

I'd rather not use polyfills just to create this alert, since the whole idea is to finally stop supporting IE.

Is there any way to achieve this?