Wrapper Object--javascript The reason that the original type owns the property

Let's look at the code first:

var s = "Test"; var len=s.length;

We know that the string declared in JavaScript like above is not an object, but since S is not an object, why is there a property of length?

The reason is that in JavaScript, whenever you reference a property of a string (numeric, Boolean, and so on), JS converts the string to an object by calling new string (s), which inherits the string's method and is used to handle the property's reference. Once the attribute reference is finished, the newly created object is destroyed (the real implementation is not necessarily the case, but the whole process looks like this). This process is called the wrapper object.

Is there a way to verify the above explanation, we look at two pieces of code:

Code One:

var s = "Test"; s.len=10;//creates a string object and adds the Len attribute, then destroys var t = s.len;//Creates a string object, reads the Len property, and the result is undefined because it does not exist

Code two:

var s = new String ("Test"); S.len = 10;var T = S.LEN;//10

The last thing to note is that the original object and the wrapper object are not strictly equal:

var s = "Test", S=new String ("test"), console.log (s = = s);//trueconsole.log (s = = = s);//false

Wrapper Object--javascript The reason that the original type owns the property