What does || {} means in JavaScript? [duplicate]

Question

I am confused with this code that I found in the Google Maps API:

window.google = window.google || {};
google.maps = google.maps || {};

And other code that I saw in a book:

var QQ = QQ || {};

What does it mean?

Why should we print that code at beginning of the JavaScript file?

Answer 1

This means that if window.google doesn't have value (undefined, null) then use {}.

It is a way of assigning a default value to a variable in JavaScript.