JavaScript constructors with objects

Question

I began to learn more about how to use JavaScript objects, and I tried to write an object in JavaScript that allows me to set some constructor arguments during initialization.

I have to say that there are several different “ design patterns ” in JavaScript that are probably mixed with syntax and much more. Through my research, I have found various StackOverflow articles, such as:

• JavaScript constructors using symbolic notation of JavaScript objects
• Constructors in JavaScript Objects

What I would like to do with my object, set some internal / private variables at the initialization point, as shown below:

<script> var TestObj = new Dispatch( 100 ); console.log( TestObj.getConstructorValue() ); //Would Return 100. </script> 

Although at the present time the method of creating the object currently Test returns undefined when trying to access it after its initialization:

 <script> $(document).on('ready', function(){ var TestObj = new Dispatch( 100 ); //Set post-initialised variables & set to '5' TestObj.setOrderNumber( 5 ); //Retrieves 5 console.log( "Accessing Property: " + TestObj.OrderNumber ); //Method for getting orderNumber Property, Returns 5 console.log( "Method for Order Number: " + TestObj.getOrderNumber() ); //Method for getting would-be constructor value console.log( TestObj.getTest() ); //Returns Undefined console.log( TestObj.Test ); //Returns Undefined }); </script> 

Javascript

 <script> /** * **/ var Dispatch = function( Arg1 ) { var OrderNumber; var Test; var setOrderNumber = function( orderNum ) { this.OrderNumber = orderNum; }; this.constructor = function( str ) { this.Test = str; }; this.constructor( Arg1 ); return { /** * Getter for OrderNumber **/ getOrderNumber : function(){ return this.OrderNumber; }, /** * Setter for OrderNumber **/ setOrderNumber : setOrderNumber, /** * Getter for Test **/ getTest : function() { return this.Test; } }; }; </script> 

What I tried (1)

I tried installing it directly:

 <script> var Dispatch = function( s ) { /** * Assign constructor * to Test **/ var Test = s; return { getTest : function() { return this.Test; } } }; TestObj.getTest(); //Returns undefined </script> 

What I tried (2)

I also tried to access the variable by slightly mixing the return function:

 <script> var Dispatch = function( s ) { var Test; var getTestVar = function() { return this.Test; } this.constructor = function( str ) { this.Test = str; }; /** * **/ this.constructor( s ); return { getTest : getTestVar }; }; TestObj.getTest(); //Returns undefined </script> 

I played with other methods, although it would be nice to get a written understanding of why I did the wrong thing to get my constructor to work.

Here's a jsFiddle that shows it all in action. I apologize for the rather long post and my ignorance of the JavaScript object!

Answer 1

You really confused many concepts.
This is what you are looking for:

 var Dispatch = function( s ) { /** * Assign constructor * to Test **/ this.Test = s; this.getTest = function() { return this.Test; } }; 

Thus:

 TestObj = new Dispatch(7); 

Result:

 Dispatch {Test: 7, getTest: function} 

and:

 TestObj.getTest(); 

Will return 7.

You can look here for more correct information about designers:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor

Answer 2

You can use this template.

 function myObject (param1) { var myPrivateMemberValue1 = param1; return { getPrivateMemberValue1: function() { return myPrivateMemberValue1; } }; } console.log(new myObject("thefourtheye")); console.log(new myObject("thefourtheye").getPrivateMemberValue1()); 

Exit

 { getPrivateMemberValue1: [Function] } thefourtheye 

Explanation:

Here we use closure . When a parameter is passed to the constructor, it is stored in a local variable. Then we return an object with the getPrivateMemberValue1 function, which still has access to the variable, which is local to the function, due to closure. That way you can make variables like this.

Answer 3

  function Dispatch(s) { var test = s; this.returnTest = function () { return test; } } var no = new Dispatch(5); no.returnTest(); // 5 

There is no direct access to the test variable because it is not a member of the newly created object, but you can access it in closure.