block8.ts

const watchers: (() => any)[] = []
const watch = (callback: () => any) => {
  callback() // this is what Vue 3 watch() will do
  watchers.push(callback)
}

const reactive = <T extends object>(t: T): T => {
  return new Proxy(t, {
    set(target, key: keyof T, value) {
      target[key] = value 

      watchers.forEach(watcher => watcher())

      return true
    },
  
    get(target, key: keyof T) {
      return target[key]
    },
  })
}