URL

The url module provides utilities for URL resolution and parsing. It can be accessed using:

const url = require('url');

URL Strings and URL Objects

A URL string is a structured string containing multiple meaningful components. When parsed, a URL object is returned containing properties for each of these components.

The following details each of the components of a parsed URL. The example 'http://user:[email protected]:8080/p/a/t/h?query=string#hash' is used to illustrate each.

┌─────────────────────────────────────────────────────────────────────────────┐
│                                    href                                     │
├──────────┬┬───────────┬─────────────────┬───────────────────────────┬───────┤
│ protocol ││   auth    │      host       │           path            │ hash  │
│          ││           ├──────────┬──────┼──────────┬────────────────┤       │
│          ││           │ hostname │ port │ pathname │     search     │       │
│          ││           │          │      │          ├─┬──────────────┤       │
│          ││           │          │      │          │ │    query     │       │
"  http:   // user:pass @ host.com : 8080   /p/a/t/h  ?  query=string   #hash "
│          ││           │          │      │          │ │              │       │
└──────────┴┴───────────┴──────────┴──────┴──────────┴─┴──────────────┴───────┘
(all spaces in the "" line should be ignored -- they are purely for formatting)

urlObject.href

The href property is the full URL string that was parsed with both the protocol and host components converted to lower-case.

For example: 'http://user:[email protected]:8080/p/a/t/h?query=string#hash'

urlObject.protocol

The protocol property identifies the URL's lower-cased protocol scheme.

For example: 'http:'

urlObject.slashes

The slashes property is a boolean with a value of true if two ASCII forward-slash characters (/) are required following the colon in the protocol.

urlObject.host

The host property is the full lower-cased host portion of the URL, including the port if specified.

For example: 'host.com:8080'

urlObject.auth

The auth property is the username and password portion of the URL, also referred to as "userinfo". This string subset follows the protocol and double slashes (if present) and precedes the host component, delimited by an ASCII "at sign" (@). The format of the string is {username}[:{password}], with the [:{password}] portion being optional.

For example: 'user:pass'

urlObject.hostname

The hostname property is the lower-cased host name portion of the host component without the port included.

For example: 'host.com'

urlObject.port

The port property is the numeric port portion of the host component.

For example: '8080'

urlObject.pathname

The pathname property consists of the entire path section of the URL. This is everything following the host (including the port) and before the start of the query or hash components, delimited by either the ASCII question mark (?) or hash (#) characters.

For example '/p/a/t/h'

No decoding of the path string is performed.

urlObject.search

The search property consists of the entire "query string" portion of the URL, including the leading ASCII question mark (?) character.

For example: '?query=string'

No decoding of the query string is performed.

urlObject.path

The path property is a concatenation of the pathname and search components.

For example: '/p/a/t/h?query=string'

No decoding of the path is performed.

urlObject.query

The query property is either the query string without the leading ASCII question mark (?), or an object returned by the querystring module's parse() method. Whether the query property is a string or object is determined by the parseQueryString argument passed to url.parse().

For example: 'query=string' or {'query': 'string'}

If returned as a string, no decoding of the query string is performed. If returned as an object, both keys and values are decoded.

urlObject.hash

The hash property consists of the "fragment" portion of the URL including the leading ASCII hash (#) character.

For example: '#hash'

url.format(urlObject)

• urlObject <Object> | <string> A URL object (as returned by url.parse() or constructed otherwise). If a string, it is converted to an object by passing it to url.parse().

The url.format() method returns a formatted URL string derived from urlObject.

If urlObject is not an object or a string, url.format() will throw a TypeError.

The formatting process operates as follows:

• A new empty string result is created.
• If urlObject.protocol is a string, it is appended as-is to result.
• Otherwise, if urlObject.protocol is not undefined and is not a string, an Error is thrown.
• For all string values of urlObject.protocol that do not end with an ASCII colon (:) character, the literal string : will be appended to result.
• If either of the following conditions is true, then the literal string // will be appended to result:
  • urlObject.slashes property is true;
  • urlObject.protocol begins with http, https, ftp, gopher, or file;
• If the value of the urlObject.auth property is truthy, and either urlObject.host or urlObject.hostname are not undefined, the value of urlObject.auth will be coerced into a string and appended to result followed by the literal string @.
• If the urlObject.host property is undefined then:
  • If the urlObject.hostname is a string, it is appended to result.
  • Otherwise, if urlObject.hostname is not undefined and is not a string, an Error is thrown.
  • If the urlObject.port property value is truthy, and urlObject.hostname is not undefined:
    • The literal string : is appended to result, and
    • The value of urlObject.port is coerced to a string and appended to result.
• Otherwise, if the urlObject.host property value is truthy, the value of urlObject.host is coerced to a string and appended to result.
• If the urlObject.pathname property is a string that is not an empty string:
  • If the urlObject.pathname does not start with an ASCII forward slash (/), then the literal string '/' is appended to result.
  • The value of urlObject.pathname is appended to result.
• Otherwise, if urlObject.pathname is not undefined and is not a string, an Error is thrown.
• If the urlObject.search property is undefined and if the urlObject.query property is an Object, the literal string ? is appended to result followed by the output of calling the querystring module's stringify() method passing the value of urlObject.query.
• Otherwise, if urlObject.search is a string:
  • If the value of urlObject.search does not start with the ASCII question mark (?) character, the literal string ? is appended to result.
  • The value of urlObject.search is appended to result.
• Otherwise, if urlObject.search is not undefined and is not a string, an Error is thrown.
• If the urlObject.hash property is a string:
  • If the value of urlObject.hash does not start with the ASCII hash (#) character, the literal string # is appended to result.
  • The value of urlObject.hash is appended to result.
• Otherwise, if the urlObject.hash property is not undefined and is not a string, an Error is thrown.
• result is returned.

url.parse(urlString[, parseQueryString[, slashesDenoteHost]])

• urlString <string> The URL string to parse.
• parseQueryString <boolean> If true, the query property will always be set to an object returned by the querystring module's parse() method. If false, the query property on the returned URL object will be an unparsed, undecoded string. Defaults to false.
• slashesDenoteHost <boolean> If true, the first token after the literal string // and preceding the next / will be interpreted as the host. For instance, given //foo/bar, the result would be {host: 'foo', pathname: '/bar'} rather than {pathname: '//foo/bar'}. Defaults to false.

The url.parse() method takes a URL string, parses it, and returns a URL object.

url.resolve(from, to)

• from <string> The Base URL being resolved against.
• to <string> The HREF URL being resolved.

The url.resolve() method resolves a target URL relative to a base URL in a manner similar to that of a Web browser resolving an anchor tag HREF.

For example:

url.resolve('/one/two/three', 'four');         // '/one/two/four'
url.resolve('http://example.com/', '/one');    // 'http://example.com/one'
url.resolve('http://example.com/one', '/two'); // 'http://example.com/two'

Escaped Characters

URLs are only permitted to contain a certain range of characters. Spaces (' ') and the following characters will be automatically escaped in the properties of URL objects:

< > " ` \r \n \t { } | \ ^ '

For example, the ASCII space character (' ') is encoded as %20. The ASCII forward slash (/) character is encoded as %3C.