The other reply is right, to clarify String({}) === "[object Object]"
I think the actual video was a little misleading, [] + {} == the string "[object Object]" not an object. The square brackets are just part of the tostring method and are unrelated to the square brackets of arrays.
I think the actual video was a little misleading, [] + {} == the string "[object Object]" not an object. The square brackets are just part of the tostring method and are unrelated to the square brackets of arrays.