What does it mean by “actions are taken” in ECMAScript 5?

Question

Here is the excerpt.

15.2.2.1 new Object ( [ value ] ) # Ⓣ
When the Object constructor is called with no arguments or with one argument value, the following steps are taken:

If value is supplied, then If Type(value) is Object, then

If the value is a native ECMAScript object, do not create a new object but simply return value.

If the value is a host object, then actions are taken and a result is returned in an implementation-dependent manner that may depend on the host object.

I'm just wondering what's the different between passing in a Native Object and passing in a Host Object to the Object constructor. In other words, if I call new Object(document), what happens behind the scene? I cannot see any difference by checking the return value.

Thanks in advance.

Answer 1

For the native objects : javascript has not to create the new object and simply returns the values.

But for the host objects : javascript first create a new object and then only returns the values.

That's what the spec is saying. Hope you understand!

Answer 2

What the excerpt is saying is that if value is a host object such as a Document , then it's up to the implementation to decide what new Object(value) will do ("actions are taken […] in an implementation-dependent manner that may depend on" value ) and what value it will return ("a result is returned in an implementation-dependent manner that may depend on" value ).

Even if value is a host object, most of the time new Object(value) will do nothing and return value (just as if it were a native object). And in the specific case of a Document , I would strongly expect that behavior. But the ECMAScript standard does not require this. (And the DOM specification, which defines the Document type, doesn't seem to require it, either.)