Why caching matters in Node.js - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to store a value in the cache object.

Node.js

cache['user'] = [1];

Drag options to blanks, or click blank then click option'

Anull

BfetchData()

C'John'

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function call instead of a value

Assigning undefined or null

We assign the string 'John' to the cache key 'user' to store the value.

2fill in blank

medium

Complete the code to check if the cache has a stored value for 'user'.

Node.js

if (cache.hasOwnProperty([1])) {
  console.log('Cache hit');
}

Drag options to blanks, or click blank then click option'

A'user'

B'cache'

C'data'

D'value'

Attempts:

3 left

💡 Hint

Common Mistakes

Checking wrong key names

Using variables instead of string keys

We check if the cache has the key 'user' to know if the data is cached.

3fill in blank

hard

Fix the error in the code to retrieve cached data safely.

Node.js

const userData = cache[1];

Drag options to blanks, or click blank then click option'

A['user']

B.get(

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot notation with a string key

Using parentheses like a function call

Accessing cache with square brackets and the key string retrieves the cached value.

4fill in blank

hard

Fill both blanks to create a cache check and fallback fetch.

Node.js

const data = cache[1] [2] fetchFromDB();

Drag options to blanks, or click blank then click option'

A['item']

B||

C&&

D??

Attempts:

3 left

💡 Hint

Common Mistakes

Using && which requires both to be true

Using ?? which only checks for null or undefined

We access cache['item'] and use || to fetch from DB if cache is empty or falsey.

5fill in blank

hard

Fill all three blanks to implement a simple cache update after fetching data.

Node.js

if (!cache[1]) {
  cache[2] = fetchData();
}
return cache[3];

Drag options to blanks, or click blank then click option'

A['key']

D['data']

Attempts:

3 left

💡 Hint

Common Mistakes

Using different keys for check and assign

Forgetting to assign fetched data to cache

We check if cache['key'] is missing, then store fetched data in cache['key'], and finally return cache['key'].