Question

What's the output?

function getAge() {
  'use strict';
  age = 21;
  console.log(age);
}

getAge();

• A: 21
• B: undefined
• C: ReferenceError
• D: TypeError

Answer 1

Answer: C

With "use strict", you can make sure that you don't accidentally declare global variables. We never declared the variable age, and since we use "use strict", it will throw a reference error. If we didn't use "use strict", it would have worked, since the property age would have gotten added to the global object.