Introduction to JavaScript URL Object
Atta
Posted on September 8, 2019
This post was originally published on attacomsian.com/blog.
The vanilla JavaScript URL
object is used to parse, construct, normalize, and encode URLs. It provides static methods and properties to easily read and modify different components of the URL.
Creating a URL
You can create a new URL
object by either passing the string URL or by providing a relative path and a base string URL to its constructor:
// url object with absolute path
const url1 = new URL('https://attacomsian.com/blog/javascript-url-object');
// url object with relative path and base url
const url2 = new URL('/blog/javascript-url-object', 'https://attacomsian.com');
In the example above, both URLs are same. We can even create a new URL based on the path relative to an existing URL:
// create new url based on existing url
const url3 = new URL('/blog', url1);
console.log(url3.toString()); // https://atttacomsian.com/blog
URL Properties
The URL
object is very helpful if you want to extract different parts from a string URL, such as the host name, port, relative path, and parameter values. You can access these properties immediately after the URL
object is created:
const url = new URL('https://attacomsian.com/blog/javascript-url-object#url-properties');
console.log(url.protocol); // https:
console.log(url.host); // attacomsian.com
console.log(url.pathname); // /blog/javascript-url-object
console.log(url.hash); // #url-properties
console.log(url.origin); // https://attacomsian.com
In addition to the above properties, the URL
object also has:
-
search
— The query parameters string including the leading?
character. -
href
— The complete URL, same asurl.toString()
method. -
port
— Returns the port of the URL. -
searchParams
— AURLSearchParams
object that can be used to access the individual query parameters found insearch
. -
username
&password
— Only available if HTTP authentication is used.
Apart from the above properties, the URL
object also provides two methods:
-
toString()
— It is similar tourl.href
but cannot be used to modify the value. -
toJSON()
— It returns the same string ashref
property.
Updating a URL
The URL
object properties (except origin
and searchParams
) can be used to construct a new URL or update parts of an existing URL:
// construct a url
const url = new URL('http://attacomsian.com');
url.pathname = '/blog/javascript-url-object';
url.hash = '#url-properties';
// update `protocol` property
url.protocol = 'https:';
console.log(url.toString()); // https://attacomsian.com/blog/javascript-url-object#url-properties
Static Methods
The URL
interface provides createObjectURL()
static method to generate a blob URL (starts with blob:
as its schema) that uniquely identify the object in the browser:
const blobUrl = URL.createObjectURL(blob);
Once you have the blob URL, pass it to revokeObjectURL()
static method to remove it from the memory:
URL.revokeObjectURL(blobUrl);
URL Object Usage
At the moment, the URL
object usage is limited. Simple strings are good enough for making network requests. However, you can use the URL
object in modern JavaScript APIs especially in Fetch API, or even in XMLHttpRequest (XHR) to communicate with the server.
Here is an example of Fetch API that uses a URL
object to get a JSON object:
const url = new URL('https://reqres.in/api/users');
fetch(url)
.then(res => res.json())
.then(res => {
res.data.map(user => {
console.log(`${user.id}: ${user.first_name} ${user.last_name}`);
});
});
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Posted on September 8, 2019
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