How do you get the URL port number of a web page when programming in JavaScript?

JavaScript has a built-in way to get this information using the Location API interface, which represents the location (URL) of the current web page you're located on. The global Window interface has access to the Location object that can be used via window.location.

Here's what the method looks like in practice:

window.location.port

This method will return a USVString containing the port number of the URL. If the URL doesn't have a port number, it will return an empty string value ("").

Here are some example returned values to expect:

// Page URL: http://localhost:3000
window.location.port = "3000"

// Page URL: https://coderrocketfuel.com:80/courses
window.location.port = "80"

// Page URL: https://coderrocketfuel.com/courses
window.location.port = ""

Notice that a URL without a port number will return an empty string value.

For more information on the browser support for this method, see its MDN web docs page.

Thanks for reading and happy coding!