URLSearchParams for query strings in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new URLSearchParams object.

Node.js

const params = new URLSearchParams([1]);

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

A{ name: 'John', age: '30' }

Bnull

C['name', 'John']

D'name=John&age=30'

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a string instead of an object.

Passing an array instead of an object.

The URLSearchParams constructor accepts an object with key-value pairs to create query parameters.

2fill in blank

medium

Complete the code to add a new parameter 'city' with value 'Paris'.

Node.js

params.[1]('city', 'Paris');

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

Aappend

Badd

Cset

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using set which replaces existing values.

Using add or push which do not exist.

The append method adds a new key-value pair to the URLSearchParams object.

3fill in blank

hard

Fix the error in the code to get the value of 'name'.

Node.js

const name = params.[1]('name');

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

AgetAll

Bfind

Cfetch

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using getAll which returns an array.

Using non-existent methods like fetch or find.

The get method returns the first value associated with the given key.

4fill in blank

hard

Fill both blanks to check if 'age' exists and then delete it.

Node.js

if (params.[1]('age')) {
  params.[2]('age');
}

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

Ahas

Bget

Cdelete

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using get to check existence which returns a value or null.

Using remove which does not exist.

The has method checks if a key exists, and delete removes it.

5fill in blank

hard

Fill all three blanks to create a query string, append a parameter, and convert to string.

Node.js

const params = new URLSearchParams([1]);
params.[2]('lang', 'en');
const queryString = params.[3]();

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

A{ page: '1', sort: 'asc' }

Bappend

CtoString

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using set instead of append when adding a parameter.

Forgetting to convert to string with toString().

We create params from an object, append a new parameter, then convert to a string with toString().

Practice

1. What does the URLSearchParams class in Node.js primarily help you do?

easy

A. Easily read and modify URL query strings

B. Create HTTP servers

C. Parse JSON data

D. Manage file system paths

Solution

1. Step 1: Understand the purpose of URLSearchParams

   URLSearchParams is designed to work with the query part of URLs, making it easy to read and change parameters.

2. Step 2: Compare with other options

   Creating servers, parsing JSON, or managing file paths are unrelated to URLSearchParams.

3. Final Answer:

   Easily read and modify URL query strings -> Option A

4. Quick Check:

   URLSearchParams = query string helper [OK]

Hint: URLSearchParams = query string helper [OK]

Common Mistakes:

• Confusing URLSearchParams with server or file system modules
• Thinking it parses JSON data
• Assuming it manages entire URLs, not just query strings

2. Which of the following is the correct way to create a URLSearchParams object from a query string in Node.js?

easy

A. const params = new URLSearchParams({name: 'John', age: 30});

B. const params = URLSearchParams('?name=John&age=30');

C. const params = URLSearchParams({name: 'John', age: 30});

D. const params = new URLSearchParams('?name=John&age=30');

Solution

1. Step 1: Check the correct syntax for creating URLSearchParams

   The constructor requires the new keyword and accepts a query string like '?name=John&age=30'.

2. Step 2: Identify incorrect options

   Options without new or passing an object directly without conversion are invalid.

3. Final Answer:

   const params = new URLSearchParams('?name=John&age=30'); -> Option D

4. Quick Check:

   Use new with query string [OK]

Hint: Always use 'new' with URLSearchParams and a query string [OK]

Common Mistakes:

• Omitting the 'new' keyword
• Passing an object directly without converting to string
• Using URLSearchParams as a function, not a constructor

3. What will the following code output?

const params = new URLSearchParams('color=blue&size=medium');
params.set('size', 'large');
console.log(params.toString());

medium

A. color=blue&size=medium

B. color=blue

C. color=blue&size=large

D. size=large&color=blue

Solution

1. Step 1: Understand params.set()

   The set method updates the value of the 'size' parameter from 'medium' to 'large'.

2. Step 2: Check the output of toString()

   The toString() method returns the query string with updated parameters in the order they were added.

3. Final Answer:

   color=blue&size=large -> Option C

4. Quick Check:

   set() updates value, toString() shows updated string [OK]

Hint: set() changes value; toString() shows updated query [OK]

Common Mistakes:

• Assuming set() adds a new parameter without replacing
• Thinking order of parameters changes
• Forgetting to call toString() to see the string

4. Identify the error in this code snippet:

const params = new URLSearchParams('page=1&limit=10');
params.append('page', 2);
console.log(params.get('page'));

medium

A. get() returns only the first 'page' value, ignoring the appended one

B. append() replaces the existing 'page' parameter instead of adding

C. URLSearchParams constructor cannot accept strings

D. append() requires both parameters to be strings

Solution

1. Step 1: Understand append() behavior

   append() adds another 'page' parameter, so now there are two 'page' keys.

2. Step 2: Understand get() behavior

   get() returns the first value for 'page', which is '1', ignoring the appended '2'.

3. Final Answer:

   get() returns only the first 'page' value, ignoring the appended one -> Option A

4. Quick Check:

   get() returns first value when duplicates exist [OK]

Hint: get() returns first value; use getAll() for all [OK]

Common Mistakes:

• Thinking append() replaces existing keys
• Expecting get() to return all values
• Assuming constructor rejects strings

5. You want to build a URL query string from an object { search: 'books', page: 2, filter: '' } but want to exclude empty values. Which code correctly creates the query string using URLSearchParams?

hard

A. const params = new URLSearchParams({ search: 'books', page: '2', filter: '' });
console.log(params.toString());

B. const params = new URLSearchParams();
for (const [key, value] of Object.entries({ search: 'books', page: 2, filter: '' })) {
if (value) params.append(key, value.toString());
}
console.log(params.toString());

C. const params = new URLSearchParams();
Object.entries({ search: 'books', page: 2, filter: '' }).forEach(([k,v]) => params.set(k,v));
console.log(params.toString());

D. const params = new URLSearchParams();
for (const key in { search: 'books', page: 2, filter: '' }) {
params.append(key, '');
}
console.log(params.toString());

Solution

1. Step 1: Understand the goal to exclude empty values

   We want to skip keys with empty strings, so we check if the value is truthy before adding.

2. Step 2: Analyze each option

   const params = new URLSearchParams({ search: 'books', page: '2', filter: '' }); console.log(params.toString()); includes empty 'filter' value. const params = new URLSearchParams(); for (const [key, value] of Object.entries({ search: 'books', page: 2, filter: '' })) { if (value) params.append(key, value.toString()); } console.log(params.toString()); adds only truthy values. const params = new URLSearchParams(); Object.entries({ search: 'books', page: 2, filter: '' }).forEach(([k,v]) => params.set(k,v)); console.log(params.toString()); adds all including empty. const params = new URLSearchParams(); for (const key in { search: 'books', page: 2, filter: '' }) { params.append(key, ''); } console.log(params.toString()); adds empty strings for all keys.

3. Final Answer:

   Option B correctly filters out empty values before appending -> Option B

4. Quick Check:

   Filter empty values before append() [OK]

Hint: Check value truthiness before adding to URLSearchParams [OK]

Common Mistakes:

• Passing object directly without filtering empty values
• Using set() without filtering, adding empty keys
• Appending empty strings for all keys