Whereas usually you can start typing an object, e.g.:

> object = {
... "a": "b",
... "c": "d"
... };
{ "a" : "b", "c" : "d" }
>

the same breaks when you try to do so with an array - with the square bracket on its own.

> array = [
Wed Aug  8 15:15:08 SyntaxError: syntax error (shell):1

It works when there's something after the square bracket, e,g.:

> array = ["a",
... "b"]
[ "a", "b" ]

or:

> array = [{
... "a":"b",
... }]
[ { "a" : "b" } ]

And fails when the remainder is concluded without the square bracket on the same line:

> array = [{
... "a":"b"
... }
Wed Aug  8 15:17:40 SyntaxError: missing ] after element list (shell):3

This only happens on the top level, as demonstrated using a nested array:

> array = [{
... "a":[
... "a"
... ]
... }]
[ { "a" : [ "a" ] } ]

I think this is to do with the V8 engine but don't really know.