Fastest way to detect external URLs

Question

What\'s the fastest method to detect if foo=\'http://john.doe\' is an external url (in comparsion to window.location.href)?

Answer 1

The main problem, is how to parse an URL, and get a host name our of it. It can be done with following way:

var _getHostname = function(url) {
  var parser = document.createElement('a');
  parser.href = url;

  return parser.hostname;
}

var isExternal = (_getHostname(window.location.href) !== _getHostname('http://john.doe'));

Or you can use is-url-external module.

var isExternal = require('is-url-external');
isExternal('http://john.doe'); // true | false 

Answer 2

You can simply use use npm package is-internal-link

Installation

npm install --save is-internal-link

Usage

import { isInternalLink } from "is-internal-link"
isInternalLink('https://www.google.com') // false
isInternalLink('/page1') // true

I also usually this with react like this

import React from 'react'

import { Link as ReactRouterLink} from 'react-router-dom'
import { isInternalLink } from 'is-internal-link'

const Link = ({ children, to, activeClassName, ...other }) => {
  if (isInternalLink(to)) {
    return (
      <ReactRouterLink to={to} activeClassName={activeClassName} {...other}>
        {children}
      </ReactRouterLink>
    )
  }
  return (
    <a href={to} target="_blank" {...other}>
      {children}
    </a>
  )
}

export default Link

Disclaimer: I am the author of this lib

Answer 3

Shouldn't

function is_external( url ) {
    return url.match( /[a-zA-Z0-9]*:\/\/[^\s]*/g ) != null;
}

do the trick? Doesn't work for absolute (internal) urls.