How to determine whether an object was created using an object literal or an Object constructor call?

Question

More specifically, how would you determine if a certain object was created using a literal or not?

var s1 = new String();
var s2 = ""; // Literal

var o1 = new Object();
var o2 = {}; // Literal

var f1 = new Function();
var f2 = function(){}; // Literal

Obviously if you compare any two above, for example:

var o1 = new Object();
var o2 = {};

alert(o1 == o2);
alert(o1 === o2);

alert(typeof o1);
alert(typeof o2);

... The first two alerts will show false while the last two alerts will give [Object object]

Say for example, if I wanted to do this:

function isLiteral(obj, type) {
    // ...
}

... how would one go about doing this?

^{I have taken a look at How to determine if an object is an object literal in Javascript?, but it does not answer my question.}

Answer 1

Firstly, the difference between these two lines:

var s1 = new String();
var s2 = ""; // Literal

...and the difference between these two lines:

var o1 = new Object();
var o2 = {}; // Literal

...are two different concepts.

The first is the difference between a primitive value and an object, while the second is... different syntax for the same thing.

---

Strings, numbers and booleans are primitive values, not objects, but can be wrapped as objects using new String(), new Number() or new Boolean(). So for these, typeof will return different values:

var s1 = new String();
typeof s1; // "object"
var s2 = "";
typeof s2; // "string"

---

However, for Object and Function, the difference between:

var o1 = new Object();
var o2 = {};

... is in syntax only.

Both o1 and o2 have the same prototype, and the same constructor, making them indistinguishable at runtime.