Why does colon notation work in place of a dot when executing a function?

Question

I know you can use the : when

• initializing objects
• using a ternary operator
• using labels

Opening my console in a Chrome browser I can execute:

window.open('http://google.ie')

That works fine. Then I type the same but using a colon instead:

window:open('http://google.ie')

Why does using a : still work and execute the open function?

Answer 1

The : makes window into a label rather than a variable:

window:
    open('...');

continue window;

And, since window is the global object in browsers, open() is a global function and can be directly referenced with or without it.

// both work
window.open('...');
open('...');

But, it's not a complete replacement for all objects and their properties:

var o = { foo: 'bar' };

o:foo // ReferenceError: foo is not defined