Document: location property

The Document.location read-only property returns a Location object, which contains information about the URL of the document and provides methods for changing that URL and loading another URL.

Though Document.location is a read-only Location object, you can also assign a string to it. This means that you can work with document.location as if it were a string in most cases: document.location = 'http://www.example.com' is a synonym of document.location.href = 'http://www.example.com'. If you assign another string to it, browser will load the website you assigned.

To retrieve just the URL as a string, the read-only document.URL property can also be used. 这个在不属于任何 browsing context 时，返回的时曾经的 url。区别于下面 null。iframe环境下，先拿到 doc，再导航，此时 doc 脱离了 context，属于垃圾对象。处于 context 时，doc.location === window.location, 指向同一对象。

If the current document is not in a browsing context, the returned value is null.

console.log(document.location);
// Prints a Location object to the console