Proof of concept of hijacking individual keys directly in an object and assigning them change callbacks

hijack.js

values = Symbol("values")
hijack = (object, callbacks) => {
  const val = object[values] ||= Object.create(null)
  Object.entries(callbacks).forEach(([key, callback]) => {
    Object.defineProperty(object, key, {
      get() { return val[key] },
      set(value) {
        callback(value)
        val[key] = value
        return true
      }
    })
  })
  return object
}


o = hijack({}, {
  foo: console.log,
  bar: value => console.log(`Bar: ${value}`)
})

o.foo = 20
o.bar = 30