Find and some methods in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of find method on array of objects

What is the output of the following code?

Javascript

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];

const result = users.find(user => user.id === 2);
console.log(result);

A undefined

B { id: 2, name: 'Bob' }

C { id: 3, name: 'Charlie' }

D [{ id: 2, name: 'Bob' }]

💡 Hint

The find method returns the first element that matches the condition.

The find method returns the first object where user.id equals 2, which is { id: 2, name: 'Bob' }.

❓ Predict Output

intermediate

Output of some method with condition

What does the following code output?

Javascript

const numbers = [1, 3, 5, 7, 8];
const hasEven = numbers.some(num => num % 2 === 0);
console.log(hasEven);

A true

B false

C undefined

D TypeError

💡 Hint

The some method returns true if any element matches the condition.

The array contains 8, which is even, so some returns true.

❓ Predict Output

advanced

Find method with no matching element

What is the output of this code?

Javascript

const fruits = ['apple', 'banana', 'cherry'];
const found = fruits.find(fruit => fruit.length > 10);
console.log(found);

A null

B '' (empty string)

C undefined

D TypeError

💡 Hint

If find does not find any element, it returns undefined.

No fruit has length greater than 10, so find returns undefined.

❓ Predict Output

advanced

Some method with all elements failing condition

What will this code output?

Javascript

const ages = [21, 25, 30];
const hasMinor = ages.some(age => age < 18);
console.log(hasMinor);

A SyntaxError

B true

C undefined

D false

💡 Hint

some returns false if no elements satisfy the condition.

No age is less than 18, so some returns false.

🧠 Conceptual

expert

Understanding behavior of find and some with complex conditions

Given the code below, what is the output of the console.log statement?

Javascript

const data = [
  { id: 1, active: false },
  { id: 2, active: false },
  { id: 3, active: true },
  { id: 4, active: true }
];

const result = data.find(item => item.active && item.id > 3);
const check = data.some(item => item.active && item.id <= 3);
console.log(result, check);

A { id: 4, active: true } true

B { id: 3, active: true } false

C undefined true

D undefined false

💡 Hint

find returns the first element matching the condition; some returns true if any element matches.

find looks for active true and id > 3, which is { id: 4, active: true }. some checks if any active true with id <= 3, which is { id: 3, active: true }, so true.