JSON as standard format in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this JSON parsing code?

Consider this JavaScript code that parses a JSON string and accesses a property.

What will be logged to the console?

Rest API

const jsonString = '{"name": "Alice", "age": 30}';
const obj = JSON.parse(jsonString);
console.log(obj.name);

A Alice

B undefined

C SyntaxError

D null

💡 Hint

Think about what JSON.parse does to a JSON string.

JSON.parse converts a JSON string into a JavaScript object. Accessing obj.name returns the value 'Alice'.

🧠 Conceptual

intermediate

Why is JSON preferred as a standard format in REST APIs?

Which of the following is the main reason JSON is widely used as a standard format in REST APIs?

A It requires special software to read

B It supports complex binary data natively

C It is human-readable and easy to parse by machines

D It is only compatible with JavaScript

💡 Hint

Think about readability and compatibility.

JSON is text-based, easy for humans to read and for machines to parse, making it ideal for data exchange.

🔧 Debug

advanced

What error does this JSON parsing code produce?

What error will this JavaScript code produce when run?

Rest API

const badJson = '{name: "Bob", age: 25}';
const data = JSON.parse(badJson);

A No error, data contains the object

B SyntaxError: Unexpected token n in JSON at position 1

C ReferenceError: badJson is not defined

D TypeError: Cannot read property 'name' of undefined

💡 Hint

Check the JSON string format carefully.

JSON keys must be in double quotes. Missing quotes cause a SyntaxError during parsing.

❓ Predict Output

advanced

What is the output of this REST API JSON response handling code?

Given this JavaScript code snippet that fetches JSON data from an API, what will be logged?

Rest API

async function getUser() {
  const response = await fetch('https://api.example.com/user');
  const data = await response.json();
  console.log(data.active);
}

// Assume the API returns: {"id": 1, "name": "Eve", "active": false}
getUser();

A false

B SyntaxError

C undefined

D true

💡 Hint

Look at the value of the 'active' property in the JSON response.

The API returns active as false, so logging data.active outputs false.

🚀 Application

expert

How many keys are in this JSON object after parsing?

Consider this JSON string and the code that parses it.

How many keys does the resulting object have at the top level?

Rest API

const jsonStr = '{"user": {"id": 10, "name": "Sam"}, "status": "active", "roles": ["admin", "user"]}';
const obj = JSON.parse(jsonStr);
console.log(Object.keys(obj).length);

A 5

B 2

C 4

D 3

💡 Hint

Count only the keys at the top level of the object.

The top-level keys are 'user', 'status', and 'roles', totaling 3 keys.