URLSearchParams for query strings in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this code using URLSearchParams?

Consider the following Node.js code snippet that uses URLSearchParams. What will be printed to the console?

Node.js

const params = new URLSearchParams('name=alice&age=30&city=NY');
console.log(params.get('age'));

A "NY"

B "alice"

C null

D "30"

💡 Hint

Remember that get returns the value of the given key from the query string.

The get method returns the value associated with the given key. Here, age is "30".

📝 Syntax

intermediate

Which option correctly creates a URLSearchParams object from an object?

You want to create a URLSearchParams instance from this object: { foo: 'bar', count: 5 }. Which code snippet works without error?

A new URLSearchParams([['foo', 'bar'], ['count', '5']])

B new URLSearchParams({ foo: 'bar', count: 5 })

C new URLSearchParams('foo=bar&count=5')

D new URLSearchParams({ foo: 'bar', count: '5' })

💡 Hint

URLSearchParams accepts a string or an iterable of key-value pairs, not a plain object.

Only option A uses an iterable of key-value pairs (array of arrays), which is valid. Options B and D pass plain objects, which cause a TypeError. Option A uses a string, which works but is not from an object.

🔧 Debug

advanced

Why does this code throw a TypeError?

Examine the code below. Why does it throw a TypeError?

Node.js

const params = new URLSearchParams({ key: 'value' });
console.log(params.toString());

A URLSearchParams constructor does not accept plain objects, only strings or iterable key-value pairs

B The toString method is not defined on URLSearchParams instances

C The key 'key' is reserved and cannot be used in URLSearchParams

D The value 'value' must be a number, not a string

💡 Hint

Check the allowed argument types for URLSearchParams constructor.

The constructor expects a string or iterable of pairs. Passing a plain object causes a TypeError.

❓ state_output

advanced

What is the final query string after these operations?

Given the following code, what will params.toString() output?

Node.js

const params = new URLSearchParams('a=1&b=2&c=3');
params.set('b', '20');
params.append('d', '4');
params.delete('a');

A "a=1&b=20&c=3"

B "b=20&c=3&d=4"

C "b=2&c=3&d=4"

D "a=1&b=20&c=3&d=4"

💡 Hint

Remember that set replaces the value, append adds a new value, and delete removes the key.

After deleting 'a', setting 'b' to '20', and appending 'd=4', the query string is 'b=20&c=3&d=4'.

🧠 Conceptual

expert

Which option correctly explains how URLSearchParams handles multiple values for the same key?

If a query string contains multiple values for the same key, how does URLSearchParams behave when using get and getAll methods?

A <code>get</code> returns the last value; <code>getAll</code> returns only the first value

B <code>get</code> returns all values as a comma-separated string; <code>getAll</code> returns the last value

C <code>get</code> returns the first value; <code>getAll</code> returns all values as an array

D <code>get</code> throws an error if multiple values exist; <code>getAll</code> returns all values

💡 Hint

Think about how to retrieve one or all values for a repeated key.

get returns the first value for a key. getAll returns an array of all values for that key.