Check if two URLs are on the same origin

Two URLs are considered to be on the same origin if they have the same protocol, host, and port. This is an important concept in web security, as it determines whether a web page can access resources from another page.

In order to determine if two URLs are on the same origin, we can easily use URL.protocol, URL.host, and URL.port to compare the properties of the two URLs. If all three properties match, the URLs are on the same origin. Otherwise, they are not.

const isSameOrigin = (origin, destination) =>
  origin.protocol === destination.protocol && origin.host === destination.host && origin.port === destination.port;

const origin = new URL('https://www.30secondsofcode.org/about');
const destination = new URL('https://www.30secondsofcode.org/contact');
isSameOrigin(origin, destination); // true
const other = new URL('https://developer.mozilla.org');
isSameOrigin(origin, other); // false