敢挑战这3道 JavaScript 题吗

function crazyFunction() {
  var a = (b = 10);
}
crazyFunction();
console.log("b", typeof b === "undefined");
console.log("a", typeof a === "undefined");

const numbers = [1, 2, 3];
for (var index = 0; index < numbers.length; index++);{
  const number = numbers[index];
  console.log(number);
}

let i;
for (i = 0; i < 3; i++) {
  const log = () => {
    console.log(i);
  };
  setTimeout(log, 100);
}

1. b false
   a true
2. undefined
3. 3
   3
   3

b  true
a  false

1
2
3

for (var index = 0; index < numbers.length; index++); // 这里多了分号，真是考察眼力呀