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NodeJS - url.format() Method

The NodeJS url.format() method returns a formatted URL string that is derived from the urlObject.

The urlObject can have the following properties

  • protocol: This specifies the protocol scheme of the URL (ex: https:).

  • slashes: A Boolean value that specifies whether the protocol is followed by two ASCII forward slashes (//).

  • auth: This specifies the authentication segment of the URL (ex: username: password).

  • username: This specifies the username from the authentication segment.

  • password: This specifies the password from the authentication segment.

  • host: This specifies the host name with the port number.

  • hostname: This specifies the host name excluding the port number.

  • port: Indicates the port number.

  • pathname: Indicates the URL path.

  • query: This contains a parsed query string unless parsing is set to false.

  • hash: It specifies the fragment portion of the URL including the “#”.

  • href: It specifies the complete URL.

  • origin: It specifies the origin of the URL.

Syntax

Following is the syntax of the NodeJS url.format() method

url.format(urlObject)

Parameters

  • urlObject: This specifies an URL object (that is returned by the parse() method or constructed otherwise).

Return Value

This method accepts a parsed URL and returns a formatted URL string.

The formatting process is done by the NodeJS url.format() method is as follows

  • Firstly, a new empty string (consider “result”) is created.

  • urlObject.protocol

    • If the urlObject.protocol is a string, it will be appended to the result. Otherwise, if the urlObject.protocol is not a string or not undefined, an Error will be thrown.

    • If the urlObject.protocol does not end with an ASCII colon (:) character, then a literal string (:) will be appended to the result.

  • urlObject.slashes

    • This specifies a Boolean value.

    • The literal string (//) will be appended to the result if either of the following conditions is true.

    • If the urlObject.slashes is true.

    • If the urlObject.protocol is http, https, ftp, gopher, or file.

  • urlObject.auth

    • If the urlObject.auth is not undefined and either urlObject.host or urlObject.hostname is not undefined, then the value of urlObject.auth is coerced into a string and appended to the result followed by the literal string “@”.

  • urlObject.host

    • If the urlObject.host is a string, it will be appended to the result. Else, if not undefined and is not a string, a TypeError will be thrown.

    • If urlObject.host is undefined, then urlObject.hostname is considered.

  • urlObject.hostname

    • If the urlObject.hostname is a string, it will be appended to the result. Else, if not undefined and is not a string, a TypeError is thrown.

  • urlObject.port

    • If the hostname is considered and urlObject.port is specified then the literal string ‘:’ will be appended to the result followed by the urlObject.port.

  • urlObject.pathname

    • If the urlObject.pathname is a string that is not empty and does not have an ASCII forward slash (/) initially, the literal string “/” will be appended to the result.

    • The value of the urlObject.hash will be appended to the result.

    • If the urlObject.hash property is not a string or not undefined, an TypeError is thrown.

  • urlObject.search

    • If the urlObject.search is a string and does not start with the ASCII question mark (?) character, the literal string ‘?’ is appended to the result.

    • The urlObject.search value will be appended to the result.

    • If urlObject.search is not undefined and is not a string, a TypeError will be thrown.

  • urlObject.query

    • If the urlObject.query is an object, then the literal string ‘?’ is appended to the result along with the querystring module stringify() method passing the value of the urlObject.query.

    • If both urlObject.search and urlObject are specified then urlObject.search will only be considered and appended to the result.

  • urlObject.hash

    • If the urlObject.hash is a string:

      • Even if the value of the urlObject.hash does not have an ASCII hash character (#) initially, the literal string “#” will be appended to the result.

      • The value of the urlObject.hash will be appended to the result.

    • Or else, if the urlObject.hash property is not a string or not undefined, a TypeError is thrown.

  • urlObject.href – This will be ignored.

  • Finally, the format() method will form a formatted URL (result).

Example

In the following example, we are parsing a URL string using NodeJS parse() method. Then we are passing the returned urlObject to the NodeJS format() method.

const url = require('url');
const address = 'https://user:pass@site.com:2000/pa/th?q=val#hash';
let urlObject = url.parse(address, true);
console.log(url.format(urlObject));

Output

As we can see in the output, the NodeJS format() method returned a formatted URL string that is derived from the urlObject.

https://user:pass@site.com:2000/pa/th?q=val#hash

Example

In the example below, we are constructing an URL object instead of parsing.

const url = require('url');
console.log(url.format({
  protocol: 'https:',
  auth: 'user:pass',
  host: 'site.com:2000',
  port: '2000',
  hostname: 'site.com',
  hash: '#hash',
  search: '?q=val',
  query: { page:'one', format: 'json'},
  pathname: '/pa/th',
  path: '/pa/th?q=val',
}))

Output

As we can see in the output below, the format() method retrieved a formatted string that is obtained from the urlObject.

https://user:pass@site.com:2000/pa/th?q=val#hash
nodejs_url_module.htm
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