Questions for JavaScript phone screen

js-phonescreen-questions.js

//What does this do? What is it called? What is it typically used for?
(function () {
  // Code
})();

//What does this do and what does it output?
function Obj() {
  this.foo = "FOO"
  this.func = function () {
    var self = this
    console.log(this.foo)
    console.log(self.foo)
    (function () {
      console.log(self.foo)
      console.log(this.foo)
    })()
  }
}

var obj = new Obj()
obj.func()

//What does this output?
;(function () {
  console.log(1)
  setTimeout(() => {
    console.log(2)
  }, 1000)
  setTimeout(() => {
    console.log(3)
  }, 0)
  console.log(4)
})()

// Do you see anything wrong w/ how this class is implemented, regarding runtime *performance*?
// How can it be optimized?

var Car = function () {
  this.revs = 0

  this.start = () => {
    this.revs = 1000
    this.status()
  };

  this.accelerate = () => {
    this.revs += 1000
    this.status()
  };

  this.decelerate = () => {
    this.revs -= 1000
    this.status()
  };

  this.status = () => {
    console.log(`revs => `, `${this.revs}RPM`)
  }
}

// This is just a simple example of how the above class may be used
var cars = []

for (var i = 0; i < 1001; i++) {
  cars.push(new Car())
}

cars[100].start()
cars[100].accelerate()
cars[100].accelerate()
cars[100].accelerate()
cars[100].decelerate()
cars[100].decelerate()