How to encode and decode a URL in JavaScript ?

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Encoding and decoding URLs in JavaScript is essential for web development, especially when making GET requests with query parameters. This process ensures special characters in URLs are correctly interpreted by the server. For instance, spaces are converted to %20 or + in URLs. This guide covers how to use JavaScript functions like encodeURI(), encodeURIComponent(), escape(), decodeURI(), decodeURIComponent(), and unescape() for effective URL encoding and decoding.

Example:

Open www.google.com and write a search query “Beginner for Beginner”.
After search results appear, observe the browser’s URL bar. The browser URL will consist of %20 or + sign in place of space.
The URL will be displayed like: https://www.google.com/search?q=Beginner%20for%20Beginner or https://www.google.com/search?q=Beginner+for+Beginner

Note: The browser converted the spaces into + or %20 signs automatically.

Encoding a URL: Encoding in Javascript can be achieved using:

Table of Content

1. JavaScript encodeURI Function
2. JavaScript encodeURIComponent() Function
3. JavaScript escape() function
1. JavaScript decodeURI() Function
2. JavaScript decodeURIComponent() Function
3. JavaScript unescape() Function
4. JavaScript querystring Module

1. JavaScript encodeURI Function

The encodeURI() function is used to encode complete URI. This function encodes the special character except for (, / ?: @ & = + $ #) characters.

Syntax:

encodeURI( complete_uri_string );

Javascript

const url = "https://www.google.com/search?q=Beginner for Beginner";
const encodedURL = encodeURI(url);
console.log(encodedURL)

Output

https://www.google.com/search?q=Beginner%20for%20Beginner

2. JavaScript encodeURIComponent() Function

The encodeURIComponent() function is used to encode some parts or components of URI. This function encodes the special characters. In addition, it encodes the following characters: , / ? : @ & = + $ #

Syntax:

encodeURIComponent( uri_string_component );

Javascript

const component = "Beginner for Beginner";
const encodedComponent = encodeURIComponent(component);
console.log(encodedComponent);

Output

Beginner%20for%20Beginner

3. JavaScript escape() function

JavaScript escape() function takes a string as a single parameter & encodes the string that can be transmitted over the computer network which supports ASCII characters. Encoding is the process of converting plain text into ciphertext.

Syntax:

escape( string )

Note: The escape() function only encodes the special characters, this function is deprecated.

Exceptions: @ – + . / * _

Javascript

const url = "https://www.google.com/search?q=Beginner for Beginner";
const encodedURL = encodeURI(url);// encoding using encodeURI
console.log(encodedURL)
console.log("<br>" + escape(url)); //encoding using escape

Output

https://www.google.com/search?q=Beginner%20for%20Beginner
<br>https%3A//www.google.com/search%3Fq%3DBeginner%20for%20Beginner

Decoding a URL

Decoding in Javascript can be achieved using

1. JavaScript decodeURI() Function

The decodeURI() function is used to decode URI generated by encodeURI().

Syntax:

decodeURI( complete_encoded_uri_string )

Example: This example describes the decodeURI() function of Javascript.

Javascript

const url = "https://www.google.com/search?q=Beginner%20for%20Beginner";
const decodedURL = decodeURI(url);
console.log(decodedURL)

Output

https://www.google.com/search?q=Beginner for Beginner

2. JavaScript decodeURIComponent() Function

The decodeURIComponent() function is used to decode some parts or components of URI generated by encodeURIComponent().

Syntax:

decodeURIComponent( encoded_uri_string_component )

Example: This example describes the decodeURIComponent() of Javascript.

Javascript

const component = "Beginner%20for%20Beginner"
const decodedComponent = decodeURIComponent(component);
console.log(decodedComponent)

Output

Beginner for Beginner

3. JavaScript unescape() Function

This function takes a string as a single parameter and uses it to decode that string encoded by the escape() function. The hexadecimal sequence in the string is replaced by the characters they represent when decoded via unescape() function.

Syntax:

unescape(string)

Note: This function only decodes the special characters, this function is deprecated.

Exceptions: @ – + . / * _

Javascript

const url = "https://www.google.com/search?q=Beginner for Beginner";
const encodedURL = encodeURI(url);
console.log(encodedURL)
console.log(escape(url));
console.log(decodeURI(encodedURL));
console.log(unescape(encodedURL));

Output

https://www.google.com/search?q=Beginner%20for%20Beginner
https%3A//www.google.com/search%3Fq%3DBeginner%20for%20Beginner
https://www.google.com/search?q=Beginner for Beginner
https://www.google.com/search?q=Beginner for ...

4. JavaScript querystring Module

The querystring module provides utilities for parsing and formatting URL query strings. It can be used to encode and decode URL components.

Encoding a URL:

To encode a URL, we can use the querystring.stringify() function to create a query string from an object and then use encodeURIComponent() to encode the resulting string.

JavaScript

const querystring = require('querystring');

const urlParams = {
    q: 'Beginner for Beginner',
    page: 1,
    sort: 'desc'
};

const encodedURL = 'https://www.google.com/search?' + querystring.stringify(urlParams);
console.log(encodedURL);

Output:

https://www.google.com/search?q=Beginner%20for%20Beginner&page=1&sort=desc

Decoding a URL:

To decode a URL, we can use the querystring.parse() function to parse the query string into an object and then access the decoded values.

JavaScript

const decodedParams = querystring.parse('q=Beginner%20for%20Beginner&page=1&sort=desc');
console.log(decodedParams.q); // Output: Beginner for Beginner
console.log(decodedParams.page); // Output: 1
console.log(decodedParams.sort); // Output: desc

Difference decodeURIComponent and decodeURI:

	decodeURIComponent	decodeURI
Definition	The decodeURIComponent() function is used to decode some parts or components of URI generated by encodeURIComponent().	Decoding in Javascript can be achieved using decodeURI function.
Syntax	decodeURIComponent( encoded_uri_string_component )	decodeURI( complete_encoded_uri_string )
Special Character Encoding	It takes encodeURIComponent(url) string so it can decode these characters.	It takes encodeURI(url) string so it cannot decoded characters (, / ? : @ & = + $ #)
Example	decodeURIComponent(“%41”) It returns “A” decodeURIComponent(“%26”): It returns “&”	decodeURI(“%41”): It returns “A” decodeURI(“%26”): It returns “%26”

URL encoding and decoding in JavaScript is crucial for seamless web development. By using functions such as encodeURI(), encodeURIComponent(), escape(), decodeURI(), decodeURIComponent(), and unescape(), developers can ensure their URLs are properly formatted and readable by servers. This skill is essential for handling query parameters in GET requests and ensures a smooth user experience on your website.

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