Swagger/OpenAPI specification in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Swagger UI middleware in an Express app.

Express

const swaggerUi = require('[1]');

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

Aswagger-express

Bswagger-ui-express

Cswagger-ui

Dexpress-swagger-ui

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'swagger-ui' which is not the Express middleware.

Using 'express-swagger-ui' which is a different package.

The correct package to serve Swagger UI in Express is swagger-ui-express.

2fill in blank

medium

Complete the code to serve the Swagger UI at the '/api-docs' route.

Express

app.use('/api-docs', swaggerUi.serve, swaggerUi.[1](swaggerDocument));

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

Aserve

Binit

Cstart

Dsetup

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'serve' which is a middleware function, not the setup method.

Using 'start' or 'init' which do not exist in this context.

The method to setup Swagger UI middleware is setup.

3fill in blank

hard

Fix the error in the Swagger document import statement.

Express

const swaggerDocument = require('./[1].json');

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

Aswagger

BswaggerDoc

CswaggerDocument

Dswagger_spec

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names instead of the actual file name.

Using camelCase names that do not match the file.

The Swagger JSON file is commonly named swagger.json.

4fill in blank

hard

Fill both blanks to create a basic Swagger document with title and version.

Express

const swaggerDocument = {
  openapi: '3.0.0',
  info: {
    title: '[1]',
    version: '[2]'
  },
  paths: {}
};

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

AMy API

B1.0.0

CAPI Docs

Dv1

Attempts:

3 left

💡 Hint

Common Mistakes

Using version as 'v1' instead of '1.0.0'.

Using generic titles that are not descriptive.

The title is usually a friendly name like 'My API', and version follows semantic versioning like '1.0.0'.

5fill in blank

hard

Fill all three blanks to define a GET endpoint '/users' with a summary and 200 response description.

Express

paths: {
  '/users': {
    get: {
      summary: '[1]',
      responses: {
        '200': {
          description: '[2]',
          content: {
            'application/json': {
              schema: [3]
            }
          }
        }
      }
    }
  }
}

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

AList all users

BSuccessful response

C{ type: 'array', items: { type: 'object' } }

DGet users

Attempts:

3 left

💡 Hint

Common Mistakes

Using vague summaries.

Leaving schema empty or incorrect.

The summary describes the endpoint action, the description explains the response, and the schema defines the data structure returned.

Practice

1. What is the main purpose of using Swagger/OpenAPI specification in an Express app?

easy

A. To speed up the server response time

B. To clearly describe and document the API endpoints and their behavior

C. To automatically fix bugs in the code

D. To encrypt the API data for security

Solution

1. Step 1: Understand Swagger/OpenAPI role

   Swagger/OpenAPI is used to describe APIs so others can understand how to use them.

2. Step 2: Identify main purpose in Express

   It helps document endpoints, request parameters, and responses clearly.

3. Final Answer:

   To clearly describe and document the API endpoints and their behavior -> Option B

4. Quick Check:

   Swagger documents APIs clearly [OK]

Hint: Swagger is for API documentation, not performance or security [OK]

Common Mistakes:

• Thinking Swagger speeds up the server
• Confusing Swagger with security tools
• Assuming Swagger fixes code bugs automatically

2. Which of the following is the correct way to set up swagger-ui-express middleware in an Express app?

easy

A. app.use('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

B. app.get('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

C. app.listen('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

D. app.post('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument));

Solution

1. Step 1: Recall Express middleware usage

   Middleware is added with app.use() for routes serving static or UI content.

2. Step 2: Identify swagger-ui-express setup

   swaggerUi.serve and swaggerUi.setup() are passed as middleware to app.use() for '/api-docs'.

3. Final Answer:

   app.use('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument)); -> Option A

4. Quick Check:

   Use app.use for middleware setup [OK]

Hint: Use app.use for middleware, not app.get or app.listen [OK]

Common Mistakes:

• Using app.get instead of app.use for middleware
• Trying to listen on a route path
• Using app.post for serving docs

3. Given this Swagger snippet in an Express app, what HTTP method and path does it describe?

{
  "paths": {
    "/users": {
      "post": {
        "summary": "Create a new user",
        "responses": {
          "201": {"description": "User created"}
        }
      }
    }
  }
}

medium

A. POST request to /users

B. DELETE request to /users

C. PUT request to /users

D. GET request to /users

Solution

1. Step 1: Read the Swagger path and method

   The snippet shows a path '/users' with a 'post' method defined.

2. Step 2: Match HTTP method and path

   The method is POST, and the path is '/users', meaning it creates a new user.

3. Final Answer:

   POST request to /users -> Option A

4. Quick Check:

   Method 'post' means POST request [OK]

Hint: Look for HTTP method keys like 'get', 'post' in paths [OK]

Common Mistakes:

• Confusing 'post' with 'get'
• Ignoring the path and focusing on responses
• Assuming default method is GET

4. You wrote this Swagger setup in your Express app but the docs page shows a blank screen:

import swaggerUi from 'swagger-ui-express';
import swaggerDocument from './swagger.json';

app.use('/docs', swaggerUi.serve, swaggerUi.setup());

What is the likely error?

medium

A. swagger.json file path is incorrect

B. Wrong import syntax for swagger-ui-express

C. Using app.use instead of app.get for docs route

D. Missing swaggerDocument argument in swaggerUi.setup()

Solution

1. Step 1: Check swaggerUi.setup() usage

   swaggerUi.setup() requires the Swagger document as an argument to display docs.

2. Step 2: Identify missing argument

   The code calls swaggerUi.setup() without passing swaggerDocument, so no docs load.

3. Final Answer:

   Missing swaggerDocument argument in swaggerUi.setup() -> Option D

4. Quick Check:

   Always pass Swagger JSON to swaggerUi.setup() [OK]

Hint: Always pass your Swagger JSON to swaggerUi.setup() [OK]

Common Mistakes:

• Forgetting to pass swaggerDocument to setup()
• Using app.get instead of app.use for middleware
• Incorrect import syntax causing silent failure

5. You want to add a new GET endpoint '/products' with a query parameter 'category' described in your Swagger file. Which snippet correctly defines this parameter in OpenAPI 3.0?

hard

A. "parameters": [{"name": "category", "in": "header", "required": false, "schema": {"type": "string"}}]

B. "parameters": [{"name": "category", "in": "path", "required": true, "schema": {"type": "string"}}]

C. "parameters": [{"name": "category", "in": "query", "required": false, "schema": {"type": "string"}, "description": "Filter products by category"}]

D. "parameters": [{"name": "category", "in": "body", "required": true, "schema": {"type": "string"}}]

Solution

1. Step 1: Identify correct parameter location for query

   Query parameters use "in": "query" and are usually optional.

2. Step 2: Check parameter details

   "parameters": [{"name": "category", "in": "query", "required": false, "schema": {"type": "string"}, "description": "Filter products by category"}] correctly sets name, in, required false, type string, and description.

3. Final Answer:

   "parameters": [{"name": "category", "in": "query", "required": false, "schema": {"type": "string"}, "description": "Filter products by category"}] -> Option C

4. Quick Check:

   Query params use "in": "query" [OK]

Hint: Query params use "in": "query", path params use "in": "path" [OK]

Common Mistakes:

• Using "in": "path" for query parameters
• Setting required true for optional query params
• Using "in": "body" which is invalid in OpenAPI 3.0