Prove That Loop in Js is Syncronus Except While Call Function Inside It

let counter1 = 0
let counter2 = 0
let counter3 = 0

console.log("Start iteration")
console.time("Time required")

// First heavy iteration
for (let i = 0; i < 1000; i++) {
  counter1 += 1
  //setTimeout(function() {console.log("AA")}, 2000)

  // Second heavy iteration
  for (let i2 = 0; i2 < 1000; i2++) {
    counter2 += 1

    // Third heavy iteration
    for (let i3 = 0; i3 < 1000; i3++) {
      counter3 += 1
    }
  }
}

console.log("Iteration was successful")
console.timeEnd("Time required")
console.log('The value of `counter1` is: ' + counter1)
console.log('The value of `counter2` is: ' + counter2)
console.log('The value of `counter3` is: ' + counter3)