Webcomponent must use immutable value to set property?

[CrabSAMA]

when i try to use web component in Vue, such as this example: https://play.vuejs.org/#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

i console log in two way:

1. es6 native class setter
2. Object.defineProperty setter
   if the property of web component changed, it will log in console

Then if i use Array.push to set value, it will do nothing, if i use imutable value to set value, it will trigger console log in web component.

I probably know why, in JavaScript complex variable is reference passing, use push did not change the reference, so it will not trigger console. Vue do some thing with Proxy to hack some action just like push, so that Vue can know the value has changed.

Now i has two question:

1. When i use web component in Vue, will I must use immutable value to set property? Is this the correct usage?
2. Can Vue reassign a property ( el[prop] = newVal ) to a component when it changes for web components?