Is this object casts or array casts?

Question

I know that：

console.log({}.length);
> undefined

console.log([].length);
> 0

console.log([] + {});
> [object Object]

but,why ([] + {}) is [object Object]

console.log(([] + {}).length);
> 15

Why...I can't figure out

Answer 1

My console gives me this:

typeof []
"object"
typeof {}
"object"
typeof [] + {}
"object[object Object]"
typeof ([] + {})
"string"

The length of your last console.log is because it is a string.