JavaScript work must Know (c) String. Where does the method come from?

String

We know that JavaScript includes: number,string,boolean,null,undefined basic type and object type.

In my cognition, the method attribute should be the object can have.

var  str= "Hello,world"; var  s=str.substring (1,4);//ell alert (typeof (str) + ":" +typeof (s));//string:string

In terms of the return type above, str is of type string.

And look at the following how to declare a string using a global object.

var c=new String (str); alert (typeof (c));//object
Alert (c.tostring ());//hello,world

Can I think: when I deal with strings,

The JavaScript compiler first uses the STR string, using new String (str), as an object. It then calls its handling and returns a string using the ToString () method.

Creation and destruction of temporary objects

From the example above I know that JavaScript creates temporary objects when processing strings, Number,boolean, and then destroys them.

   var a = "Hello,world";        var c = new String (a); A string object was created.        C.len = 4;        Alert (typeof (c));//object;        alert (C.len);//4///////////////////////////////////////////////////////////////////////         a.len=5;         alert (A.len);//undefined

A.len compiler did not error, because the temporary object created after the operation, and then destroyed.

= = and = = =

A==c;//true;a===c;//false; The string and object are unequal.

　　

JavaScript work must Know (c) String. Where does the method come from?