Context argument in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the purpose of the context argument in GraphQL resolvers?

In GraphQL, resolvers receive a context argument. What is its main purpose?

A To provide shared objects like authentication info or database connections to all resolvers during a request

B To specify the query operation type such as query or mutation

C To define the schema types and fields for the GraphQL API

D To store the results of previous resolver calls for caching

💡 Hint

Think about what information needs to be accessible to all resolvers during a single request.

The context argument is a shared object passed to every resolver during a GraphQL request. It commonly holds authentication data, database connections, or other utilities needed by resolvers.

❓ query_result

intermediate

What will be the output of this resolver using context?

Given the following resolver code snippet, what will getUserName return?

const resolvers = {
  Query: {
    getUserName: (parent, args, context) => {
      return context.user.name;
    }
  }
};

const context = { user: { id: 1, name: 'Alice' } };

// Query: { getUserName }

A undefined

B "user"

C null

D "Alice"

💡 Hint

Look at what context.user.name contains.

The resolver returns context.user.name, which is "Alice" in the provided context object.

📝 Syntax

advanced

Identify the syntax error in this resolver using context

Which option contains a syntax error in accessing the context argument in a resolver?

const resolvers = {
  Query: {
    getUserEmail: (parent, args, context) => {
      return context.user.email;
    }
  }
};

A getUserEmail: (parent, args) => { return context.user.email; }

B getUserEmail: (parent, args, context) => { return context.user.email; }

C getUserEmail: (parent, args, context) => { return context.user.email }

D } ;liame.resu.txetnoc nruter { ;tg&= )txetnoc ,sgra ,tnerap( :liamEresUteg

💡 Hint

Check if the context argument is declared properly.

Option A does not declare the context parameter, but tries to use it, causing a ReferenceError.

❓ optimization

advanced

How to optimize database access using context in GraphQL resolvers?

You want to avoid opening a new database connection in every resolver. How can you use the context argument to optimize this?

A Pass database connection as an argument in every query instead of context

B Open a new database connection inside each resolver ignoring context

C Create a single database connection in the context object and reuse it in all resolvers during the request

D Store database connection info in global variables outside context

💡 Hint

Think about sharing resources efficiently during a request.

Creating one database connection in the context and reusing it in all resolvers avoids overhead and improves performance.

🔧 Debug

expert

Why does this resolver fail to access user info from context?

Consider this resolver:

const resolvers = {
  Query: {
    currentUser: (parent, args, context) => {
      return context.userInfo;
    }
  }
};

// Context setup:
const context = { user: { id: 5, name: 'Bob' } };

// Query: { currentUser }

Why does currentUser return null or undefined?

A The resolver function signature is missing the <code>context</code> argument

B The resolver tries to access <code>context.userInfo</code> but the context only has <code>user</code> property

C The query is malformed and does not call <code>currentUser</code>

D The context object is not passed to the GraphQL server

💡 Hint

Compare the property names used in the resolver and the context object.

The resolver accesses context.userInfo but the context object only has a user property, so it returns undefined.