JavaScript new constructor and object detailed

First we disassemble to the following code
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var str = function () {                  return to ' Hello world ';            }             alert (New Str ());             var str1 = function () {                  return to New String (' Hello World ');            }             Alert (new str1 ())

This code and your previous code is a meaning, understand it.
Okay, let's do the experiment.
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var str = function () {                  return to ' Hello world ';            }             alert (str);             var str1 = function () {                  return to New String (' Hello World ');            }             alert (str1)

The printed result is expected. It's also obvious, not much explained.
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var str = function () {                  return to ' Hello world ';            }             alert (str ());             var str1 = function () {                  return to New String (' Hello World ');            }             alert (str1 ())

Well, coming down here with the meaning, the results are understandable. But why, the result of a function as a builder is different.
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function str () {                  return to ' Hello world ';            }             function str1 () {                  return to New String (' Hello World ');            }             alert (New Str ());             Alert (new str1 ());

We need to know 2 things to solve this problem.
1, new () Dry God horse thing
Many child shoes know that the new function () returns the this pointer object as an object reference. But if there is no this in the demo above, you return a value directly.

Let's look at a new example
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var test = ' Hello World '; var test1 = new String (' Hello World '); function Teststr () { return test; } function TestStr1 () { return test1; } Alert (new teststr () = = test);//outputs:false Alert (new testStr1 () = = test1); output:true

Yes, it's a bit of a feeling, but it's still confusing. Don't worry, we'll keep looking.
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Alert (test instanceof String); Alert (test1 instanceof String);

Based on the example above, we see that test is not instanceof string. You can also see that the typeof of Test is string in typeof. So we extend a question, what's the difference between a literal object and a constructor object? Answer: PROTOTYPE!!!!.
Well, we're solving the second problem, so we can push back the first question I just said, what new () did, in fact, new did something we needed to know. is to maintain the prototype chain.
Finally I make a hypothesis. Because I'm not sure that I'm right right now.
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function func () { } var test = new Func (); /* New in the process of doing the following behavior var returnval = new Object (); Returnval.prototype = this;//This step is not necessarily the case, we can understand the replication phase If (ReturnVal is Object) {//This is instanceof more appropriate, or that the prototype chain can be found inherited from the object return returnval; } else return obj; */