DataLoader integration in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import DataLoader in a NestJS service.

NestJS

import [1] from 'dataloader';

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

ADataLoad

BLoaderData

CDataLoader

DLoader

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect import names like 'LoaderData' or 'DataLoad'.

Forgetting to import DataLoader before using it.

You need to import DataLoader exactly as it is exported from the 'dataloader' package.

2fill in blank

medium

Complete the code to create a new DataLoader instance in a NestJS service.

NestJS

const userLoader = new DataLoader([1]);

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

AbatchLoadFn

BbatchLoaderFn

CloadBatchFn

DbatchLoadFunction

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names like 'batchLoadFunction' or 'loadBatchFn'.

Passing the batch function directly without wrapping in an object.

The DataLoader constructor expects an object with a batchLoadFn property that is a function to batch load keys.

3fill in blank

hard

Fix the error in the batch loading function signature for DataLoader.

NestJS

async function batchLoadUsers([1]) { return users; }

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

Akey

Bkeys

CuserIds

Dids

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular names like 'key' which is not an array.

Using unrelated parameter names that confuse the function purpose.

The batch loading function receives an array of keys, commonly named keys.

4fill in blank

hard

Fill both blanks to create a DataLoader that batches user IDs and returns users.

NestJS

const userLoader = new DataLoader(async ([1]) => {
  const users = await this.userService.findByIds([2]);
  return [1].map(id => users.find(user => user.id === id));
});

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

Akeys

BuserIds

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names between parameter and service call.

Not mapping keys to users correctly.

The batch function receives keys and passes userIds to the service. Then it maps keys to the found users.

5fill in blank

hard

Fill all three blanks to use DataLoader in a NestJS resolver method to load a user by ID.

NestJS

async getUser(id: string) {
  const user = await this.[1].load([2]);
  return user ? [3] : null;
}

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

AuserLoader

Bid

Cuser

DuserService

Attempts:

3 left

💡 Hint

Common Mistakes

Calling load on the service instead of the DataLoader.

Returning the wrong variable or forgetting to check for null.

The method calls userLoader.load(id) and returns the loaded user or null.