While objects are overrated, that's not what I'm talking about here. I didn't say "imperatively constructing objects of a type", I said "imperatively constructing types".
This has likely changed since I last used javascript, but in the bad old days, if you wanted to specify a "type" (in the structural sense- a common set of fields that you might construct instances of), you build that type with statements rather than declarations. That feels icky. Also, that means that any potential IDE has to interpret your code (rather than simply parsing declarations) to provide any real support for you, which meant it took forever for IDEs to provide things like autocomplete (let alone foolproof renaming).