`this` is no longer passed for the first argument of `this.$watch`
Dec 5th 2020
Version
3.0.4
Reproduction link
Vue 2: https://jsfiddle.net/skirtle/5mhLtuqx Vue 3: https://jsfiddle.net/skirtle/fo1bh34x
by @ skirtles-code at https://github.com/vuejs/docs-next/issues/722
Steps to reproduce
The first argument expOrFn of this.$watch (and Vue.watch) couldn't receive the first argument vm (which equals to this) any more.
What is expected?
Add the first argument back, or write this change in doc
What is actually happening?
Only this left currently since Vue 3.