Why in JS you can't assign a value to a missing property of an object, but you can assign a value to a missing nested property of an object?

Question

JavaScript

Let's say there is a certain object: Why the code Will swear that param is not defined, but if you define another property: Then it will not swear. Indeed, in both cases, there is no nested param property. Explain how it works
const someObject = { param: 'value' }
someObject.another.param = 'value'
someObject.another = {}

Answer 1

Before assigning, the compiler looks for the place of the assignment.
someObject - know where to look (this), found
.another - know where to look (someObject), not found
.param - don't know where to look, error
someObject - know where to look (this), found
.another - know where to look (someObject) , Have not found

Will swear that param is not defined

I suspect that the compiler will swear not that param is not defined, but that another (undefined) is not defined.

Answer 2

in the first option you are trying to find an apartment in a non-existent house, in the second option you are looking for an apartment that does not exist in the house. as if the first option does not make sense, therefore the error