The modern way:
new URL("http://example.com/aa/bb/")
Returns an object with properties hostname and pathname, along with a few others.
The first argument is a relative or absolute URL; if it’s relative, then you need to specify the second argument (the base URL). For example, for a URL relative to the current page:
new URL("/aa/bb/", location)
In addition to browsers, this API is also available in Node.js since v7, through require('url').URL.