Just a couple of examples. Arrays and Objects are the same type of structure in JavaScript. Arrays just happen to be indexed by integers and Objects by strings. In Java this is not the case.
Another example, in Java Classes are not objects that can be manipulated, they require a special form (generics) for that. In JavaScript a "class" is just a function that has some default properties attached.
Just a couple of examples. Arrays and Objects are the same type of structure in JavaScript. Arrays just happen to be indexed by integers and Objects by strings.
This description doesn't tell the whole story, leading people to a false conclusion of simplicity.
When it comes to JavaScript arrays, a lot of magic is happening under the covers that doesn't happen with non-array objects. Good JavaScript developers need to know those details, and that counts as complexity.
You're doing people here a disservice by leaving out relevant information.
The associative arrays in JS are simpler than objects in Java but the expressiveness means you need to be aware of all the different types of type coercion and how it all interacts at runtime. I don't think this is that difficult but it's no more difficult to lay out your data before runtime. I think this is a wash that goes to the dynamic vs static debate which we all know can be argued about for days.
You're leaving out prototypes which I find much more complicated than Java Classes.
But the discussion isn't about complexity, the discussion is about "smallness" and prototypes are definitely small. They are just "bags of properties" like all JavaScript objects. They just have the special function of being automatically applied to a new object's "__proto__" property when using new. Compare that to Java, where Classes are not objects themselves, they are blueprints for creating objects. But the distinction there means if you want to reason about Classes you need a special form in generics.
