javascript-interview-prep/exams/00-evaluation.md

JavaScript Technical Interview - Diagnostic Assessment

Purpose: Identify knowledge gaps to build a personalized 6-hour study curriculum Time: No time limit - answer based on current knowledge Instructions: Choose the best answer for each question. Do NOT research answers.

---

Section 1: Core Concepts & Fundamentals

Question 1

What will be logged?

console.log(typeof null);

• A) "null"
• B) "object"
• C) "undefined"
• D) "number"

Your answer: ___

A

---

Question 2

What is the output?

const arr = [1, 2, 3];
arr[10] = 11;
console.log(arr.length);

• A) 4
• B) 10
• C) 11
• D) undefined

Your answer: ___ C

Question 3

What gets logged?

function foo() {
  console.log(this.bar);
}
const obj = { bar: 'hello', foo };
const fn = obj.foo;
fn();

• A) "hello"
• B) undefined
• C) ReferenceError
• D) null

Your answer: ___ B

Question 4

What is the result?

console.log(0.1 + 0.2 === 0.3);

• A) true
• B) false
• C) undefined
• D) NaN

Your answer: ___ A

Section 2: Closures & Scope

Question 5

What will be logged?

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

• A) 0, 1, 2
• B) 3, 3, 3
• C) undefined, undefined, undefined
• D) 0, 0, 0

Your answer: ___ A

Question 6

What is the output?

let x = 1;
function outer() {
  let x = 2;
  function inner() {
    x++;
    console.log(x);
  }
  return inner;
}
const fn = outer();
fn();
fn();

• A) 2, 2
• B) 3, 4
• C) 2, 3
• D) 1, 2

Your answer: ___ C

Section 3: Promises & Async

Question 7

What order will be logged?

console.log('1');
setTimeout(() => console.log('2'), 0);
Promise.resolve().then(() => console.log('3'));
console.log('4');

• A) 1, 2, 3, 4
• B) 1, 4, 2, 3
• C) 1, 4, 3, 2
• D) 1, 3, 4, 2

Your answer: ___ C

Question 8

What happens here?

async function foo() {
  return 'hello';
}
console.log(foo());

• A) "hello"
• B) Promise {: "hello"}
• C) Promise {}
• D) undefined

Your answer: ___ C

Question 9

What will be the output?

Promise.resolve(1)
  .then(x => x + 1)
  .then(x => { throw new Error('error'); })
  .catch(() => 3)
  .then(x => console.log(x));

• A) 1
• B) 2
• C) 3
• D) Error is thrown

Your answer: ___ C

Section 4: Modern ES6+ Features

Question 10

What is logged?

const obj = { a: 1, b: 2, a: 3 };
console.log(obj.a);

• A) 1
• B) 2
• C) 3
• D) SyntaxError

Your answer: ___ A

Question 11

What is the result?

const arr = [1, 2, 3];
const [a, ...b, c] = arr;
console.log(b);

• A) [2]
• B) [2, 3]
• C) [1, 2, 3]
• D) SyntaxError

Your answer: ___ B

Question 12

What gets logged?

const obj = { x: 1 };
const copy = { ...obj };
copy.x = 2;
console.log(obj.x);

• A) 1
• B) 2
• C) undefined
• D) ReferenceError

Your answer: ___ A

Section 5: Objects & Prototypes

Question 13

What is the output?

const obj = Object.create(null);
console.log(obj.toString());

• A) "[object Object]"
• B) "null"
• C) undefined
• D) TypeError

Your answer: ___ C

Question 14

What will be logged?

function Person(name) {
  this.name = name;
}
Person.prototype.greet = function() {
  return `Hello ${this.name}`;
};
const p = new Person('Alice');
console.log(p.hasOwnProperty('greet'));

• A) true
• B) false
• C) undefined
• D) TypeError

Your answer: ___ A

Question 15

What is the result?

class Animal {
  constructor() {
    this.type = 'animal';
  }
}
class Dog extends Animal {
  constructor() {
    this.breed = 'labrador';
    super();
  }
}
const dog = new Dog();

• A) dog.type is "animal"
• B) dog.breed is "labrador"
• C) ReferenceError
• D) Both properties are set correctly

Your answer: ___ D

Section 6: Array Methods & Iteration

Question 16

What is the output?

const arr = [1, 2, 3, 4];
const result = arr.map(x => x * 2).filter(x => x > 5);
console.log(result);

• A) [6, 8]
• B) [3, 4]
• C) [2, 4, 6, 8]
• D) [6]

Your answer: ___ A

Question 17

What gets logged?

[1, 2, 3].reduce((acc, val) => acc + val);

• A) 6
• B) "123"
• C) [1, 2, 3]
• D) undefined

Your answer: ___ A

Question 18

What is the result?

const arr = [1, 2, 3];
arr.forEach(x => {
  if (x === 2) return;
  console.log(x);
});

• A) 1, 3
• B) 1
• C) 3
• D) Nothing is logged

Your answer: ___ A

Section 7: Event Loop & Execution

Question 19

What order will be logged?

async function foo() {
  console.log('1');
  await Promise.resolve();
  console.log('2');
}
foo();
console.log('3');

• A) 1, 2, 3
• B) 1, 3, 2
• C) 3, 1, 2
• D) 2, 1, 3

Your answer: ___ B

Question 20

What is the output?

console.log(1);
queueMicrotask(() => console.log(2));
Promise.resolve().then(() => console.log(3));
console.log(4);

• A) 1, 2, 3, 4
• B) 1, 4, 2, 3
• C) 1, 4, 3, 2
• D) 1, 3, 2, 4

Your answer: ___ B

Section 8: Tricky Scenarios & Edge Cases

Question 21

What will be logged?

const a = [1, 2, 3];
const b = [1, 2, 3];
console.log(a == b);

• A) true
• B) false
• C) undefined
• D) TypeError

Your answer: ___ A

Question 22

What is the result?

console.log([] + []);

• A) []
• B) ""
• C) undefined
• D) "[object Array][object Array]"

Your answer: ___ B

Question 23

What gets logged?

const obj = {
  value: 42,
  getValue: () => this.value
};
console.log(obj.getValue());

• A) 42
• B) undefined
• C) null
• D) ReferenceError

Your answer: ___ A

Question 24

What is the output?

console.log(+'42');

• A) "42"
• B) 42
• C) NaN
• D) undefined

Your answer: ___ B

Question 25

What will be logged?

let x = y = 10;
(function() {
  let x = y = 20;
})();
console.log(y);

• A) 10
• B) 20
• C) undefined
• D) ReferenceError

Your answer: ___ A

Submission

Fill in your answers and save this file, then run the evaluation script or notify your instructor.

Answer Key Format:

1: B
2: C
3: A
4: B
5: B
6: B
7: C
8: B
9: C
10: C
11: D
12: A
13: D
14: B
15: C
16: A
17: A
18: A
19: B
20: B
21: B
22: B
23: B
24: B
25: B