What does 0 mean: ({}) in an object dump in Mozilla Firefox

Question

I threw the object in Mozilla and I got the following:

({ length:1, prevObject:{0:({}), context:({}), length:1}, context:({}), selector:"ROOT", 0:({}) }) 

What does ({}) mean in object notation? I understand that {} means an object, but what do parentheses mean?

Answer 1

Because {} can also mean an empty block, for example: in the console you need to enter ({}) to indicate an object.