How to build a dynamic JSON object

[#1]

All, 
    I am wondering how to build a dynamic JSON object in JSL ? 

request = New HTTP Request(
	url( "http://httpbin.org/post" ),
	Method( "POST" ),
	JSON( "\[{"username":"bob","address":"12345"}]\" )
);

   Using the example from the scripting index, if I wantedt to vary the username from bob to say mark and address from 12345 to 12346 and I have 10 such calls, I would prefer building that as a dynamic object outside. I initially ventured down the path of building it as an Associative Array and then using the As JSON Expr() , however, that is resulting in an error. My approach in that case was: 

MyAA = Associative Array(); 
MyAA["username"] = "bob" ; 
MyAA["address"] = "12345" ;

request = New HTTP Request(
	url( "http://httpbin.org/post" ),
	Method( "POST" ),
	JSON( As Json Expr(MyAA)) 
);

Of course, this is not happening for this example, but the api I am trying to call on. However, when I pass hardcoded JSON as an input, the api call works as expected. 

Any help is appreciated. 

[#2]

@nascif_jmp  and @bryan_boone ,

        Thank you for your responses. Your responses helped me get somewhere, however I have a couple of questions: 

1. Can you kindly provide an example of accepted JSON array format in JSL ? Is this accepted ?

2. Does the scripting index or scripting guide cover the portions on JSON array or how to define an empty JSON object as nasicf has kindly shown ? 
   a. If yes, I would like to read that 
   b. If no, I would request that this be added to the documentation, because I couldn't find it anywhere 

[#3]

Do you have the link to the API. I don't think you've listed valid JSON.
At least the JSON Editor in Chrome doesn't think so.
Thanks

[#4]

Ah.

I had a transcribing error going from picture to text.

[#5]

If I rewrite it like this using the chrome add in JSON Editor, I see a List of Associative Arrays

[
  {
    "month": 1,
    "month_name": "Jan",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 2,
    "month_name": "Feb",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 3,
    "month_name": "Mar",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 4,
    "month_name": "Apr",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 5,
    "month_name": "May",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 6,
    "month_name": "Jun",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 7,
    "month_name": "Jul",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 8,
    "month_name": "Aug",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 9,
    "month_name": "Sep",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 10,
    "month_name": "Oct",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 11,
    "month_name": "Nov",
    "albedo": 0.2,
    "soiling_loss": 2
  },
  {
    "month": 12,
    "month_name": "Dec",
    "albedo": 0.2,
    "soiling_loss": 2
  }
]

 

[#6]

This seems to work.
innerList = {};
InsertInto(innerList, [ "month" => 1, "month_name" => "Jan", "albedo" => 0.2, "soiling_loss" => 2.0]);
InsertInto(innerList, [ "month" => 2, "month_name" => "Feb", "albedo" => 0.2, "soiling_loss" => 2.0]);
InsertInto(innerList, [ "month" => 3, "month_name" => "Mar", "albedo" => 0.2, "soiling_loss" => 2.0]);
monthlyFactors = {innerList};
je = As JSON Expr(EvalList(monthlyFactors));
Show(je);

I think the real issue is knowing the right API calls to the JSL list and associative arrays data structures, and their behavior as far as evaluating variables, returning a copy vs a live reference, and so on. The fact that they are being used to build a JSON object is incidental.

Having said that, with the new support for REST APIs from JMP I agree that having a session with a more detailed, end-to-end example would be helpful. I will pass this sugestion alone to our doc team. Thanks for the suggestion!

[#7]

And don't forget you can create JSON by just concatenating strings in the JSON format.

No Lists or Associative Arrays needed.

[#8]

That was for building it step by step, the complete "hardcoded" version would be just
monthlyFactors = { {
[ "month" => 1, "month_name" => "Jan", "albedo" => 0.2, "soiling_loss" => 2.0],
[ "month" => 2, "month_name" => "Feb", "albedo" => 0.2, "soiling_loss" => 2.0],
[ "month" => 3, "month_name" => "Mar", "albedo" => 0.2, "soiling_loss" => 2.0]
}};
je = As JSON Expr(monthlyFactors);
Show(je);
As a rule of thumb:
* JSON arrays map to JSL lists (not matrices or vectors, beware of the '[]' similarity);
* JSON dictionaries map to JSL associative arrays;
* Check for non-evaluated variable references;
* Check if data structure modifying calls actually change the target object (as opposed to returning a modified copy).