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Node | URL.format(urlObject) API
  • Last Updated : 21 May, 2019

The URL.format(urlObject) is the inbuilt API provided by URL class, which takes an object or string and return a formatted string derived from that object or string.

Syntax:

const url.format(urlObject)

If the urlObject is not an object or string, then it will throw a TypeError.
Return value: It returns string derieved from urlObject.

The urlObject can have the following fields or keys:



  • protocol
  • slashes
  • auth
  • hostname
  • host
  • port
  • pathname
  • search
  • query
  • hash

The formatting process is as follows:

      1. Initially, an empty string (‘’ say result) is created and then following parameters are looked for in order.

      2. urlObject.protocol: string

      • If urlObject.protocol is a string it is appended to the result else if not undefined and not a string then Error is thrown.
      • If urlObject.protocol do not end with ASCII colon ( : ) then, the literal ‘:’ is appended to the result.
      3. urlObject.slashes: boolean

      • If either of the following property is true, then literals ‘//’ are appended to the result:
        • urlObject.slashaes is true.
        • urlObject.protocol is http, https, ftp, gopher, or file, then slashes will be automatically true even if slashes is false.
      4. urlObject.auth: string

      • If the urlObject.auth is not undefined and urlObject.host or urlObject.hostname is also not undefined then auth is appended to the result with literal ‘@’ irrespective of whether the literal ‘@’ present or not at the end.
      5. urlObject.host: string

      • If urlObject.host is a string it is appended to the result else if not undefined and not a string then Error is thrown.
      • If it is undefined then urlObject.hostname is considered.
      6. urlObject.hostname: string

      • If urlObject.hostname is a string it is appended to the result else if not undefined and not a string then Error is thrown.
      • If both host and hostname are defined then host will be given considered.
      7. urlObject.port: (number | string)

      • If hostname is considered and urlObject.port is defined then literal ‘:’ will be appended to the result along with urlObject.port.
      8. urlObject.pathname: string



      • If urlObject.pathname is a string but not empty string and not starting with literal ‘/’, then literal ‘/’ is appended to the result.
      • urlObject.pathname is appended to the result.
      • Else UrlObject.pathname is not a string then Error is thrown.
      9. urlObject.search: string

      • If urlObject.search is a string but not empty string and not starting with literal ‘?’, then literal ‘?’ is appended to the result.
      • urlObject.search is appended to the result.
      • If urlObject.search is not a string then Error is thrown.
      10. urlObject.query: Object

      • If urlObject.query is an Object then literal ‘?’ is appended to the result along with output of calling the querystring module’s stringify() method passing the value of urlObject.query.
      • If both urlObject.search and urlObject.query are defined then urlObject.search will only be considered.
      11. urlObject.hash: string

      • If urlObject.hash is a string but not empty string and not starting with literal ‘#’, then literal ‘#’ is appended to the result.
      • urlObject.hash is appended to the result.
      • Else urlObject.hash is not a string and is not undefined then Error is thrown.
      12. Finally, the result is returned.

Example 1

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/*
  node program to demonstrate the URL.format API.
*/  
    
//importing the module 'url'
const url = require('url');
  
//creating and initializing urlObject
var urlObject={
        protocol: 'https',
        hostname: 'example.com',
        port: 1800,
        pathname: 'sample/path',
        query: {
                page: 1,
                format: 'json'
        },
        hash: 'first'
    }
  
//getting the derieved URL from urlObject using the url.format function
var sampleUrl=url.format(urlObject);
  
//Display the returned value
console.log(sampleUrl.toString());
   

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Output: https://example.com:1800/sample/path?page=1&format=json#first

Example 2

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/*
  node program to demonstrate the URL.format API.
*/  
    
//importing the module 'url'
const url = require('url');
  
//creating and initializing urlObject
var urlObject={
        protocol: 'prct',
        slashes: false,
        host: 'example.com',
        auth: 'abc',
        pathname: '/sample/path',
        search: 'something',
        hash: 'first'
    }
  
//getting the derieved URL from urlObject using the url.format function
var sampleUrl=url.format(urlObject);
  
//Display the returned value
console.log(sampleUrl.toString());

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Output: prct:abc@example.com/sample/path?something#first

NOTE: The above program will compile and run by using the node fileName.js command.

Reference:
https://nodejs.org/api/url.html#url_url_format_urlobject

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