Version

3.0.0

Reproduction link

https://jsfiddle.net/ljcremer/uLjd85va/159/

Steps to reproduce

Run the application and then change the width of the fiddle run section.

What is expected?

I expect the computed property computedWidth to change reactively

What is actually happening?

It does not change reactively

I first tried with ref but the same symptom. Also tried to use the recommended method in https://github.com/vuejs/vue-next/issues/901 but still no luck

dom properties are not reactive

This is expected behavior. Vue does not observe native DOM elements. Only plain userland objects can be made reactive.