[Vue] - a data hijacking face questions drawn ---

A face questions

What kind of a meet (a === 1 && a === 2 && a === 3) === true it? (Note that 3 =, which is strictly equal)

Object.defineProperty(window, 'a', {
  get () {
    current++
    return current
  }
})
console.log(a === 1 && a === 2 && a === 3) // true