How to Build a JSON Object

How to create JSON Object using String?

org.json.JSONArray may be what you want.

String message;
JSONObject json = new JSONObject();
json.put("name", "student");

JSONArray array = new JSONArray();
JSONObject item = new JSONObject();
item.put("information", "test");
item.put("id", 3);
item.put("name", "course1");
array.put(item);

json.put("course", array);

message = json.toString();

// message
// {"course":[{"id":3,"information":"test","name":"course1"}],"name":"student"}

Create JSON object dynamically via JavaScript (Without concate strings)

This is what you need!

function onGeneratedRow(columnsResult)
{
    var jsonData = {};
    columnsResult.forEach(function(column) 
    {
        var columnName = column.metadata.colName;
        jsonData[columnName] = column.value;
    });
    viewData.employees.push(jsonData);
 }

How to fluently build JSON in Java?

I am using the org.json library and found it to be nice and friendly.

Example:

String jsonString = new JSONObject()
                  .put("JSON1", "Hello World!")
                  .put("JSON2", "Hello my World!")
                  .put("JSON3", new JSONObject().put("key1", "value1"))
                  .toString();

System.out.println(jsonString);

OUTPUT:

{"JSON2":"Hello my World!","JSON3":{"key1":"value1"},"JSON1":"Hello World!"}

How to dynamically build a JSON object?

You build the object before encoding it to a JSON string:

import json

data = {}
data['key'] = 'value'
json_data = json.dumps(data)

JSON is a serialization format, textual data representing a structure. It is not, itself, that structure.

Best way to create this JSON object in Golang

Declare types that match the structure of the JSON document.

type client struct {
    Hostname string `json:"Hostname"`
    IP       string `json:"IP"`
    MacAddr  string `json:"MacAddr"`
}

type connection struct {
    Clients []*client `json:"Clients"`
}

Initialize values using those types and encode to JSON.

var clients []*client
for _, line := range strings.Split(line, "\n") {
    if line != "" {
        s := strings.Split(line, " ")
        clients = append(clients, &client{Hostname: s[0], IP: s[1], MacAddr: s[2]})
    }
}

p, _ := json.Marshal(connection{Clients: clients})
fmt.Printf("%s\n", p)

The JSON field tags (json:"Hostname") are not needed in this example because the JSON object keys are valid exported identifiers. I include the tags here because they are often needed.

Run the code on the Go Playground.

How to create a JSON object in Ruby

The core of your problem is that you are creating an array of JSON strings, instead of an array and then making that JSON. Instead of:

companies_json = []

data_hash.each do |hash|
  companies_json << hash.to_json
end

do:

companies = []

data_hash.each do |hash|
  companies << hash
end

companies_json = companies.to_json

How can I build this JSON object in Flutter?

This part is not correct:

newQuiz = Quiz.fromJson(newQuestion.toJson());

Think about it, newQuestion.toJson() will give you something like:

{
  "question" : "La velocidad de la luz es igual a",
  "solucion1": "300k",
  "solucion2": "250k",
  "solucion3" : "150k",
  "answer" : "300k"
}

But Quiz.fromJson() expects data to be in a format like this:

{
  "questions": [
    {
      "question" : "La velocidad de la luz es igual a",
      "solucion1": "300k",
      "solucion2": "250k",
      "solucion3" : "150k",
      "answer" : "300k"
    }
  ]
}

Maybe try:

newQuiz = Quiz(questions: [newQuestion, ...newQuiz.questions]);

Or even just this:

newQuiz.questions.add(newQuestion);

Build a JSON string with Bash variables

You are better off using a program like jq to generate the JSON, if you don't know ahead of time if the contents of the variables are properly escaped for inclusion in JSON. Otherwise, you will just end up with invalid JSON for your trouble.

BUCKET_NAME=testbucket
OBJECT_NAME=testworkflow-2.0.1.jar
TARGET_LOCATION=/opt/test/testworkflow-2.0.1.jar

JSON_STRING=$( jq -n \
                  --arg bn "$BUCKET_NAME" \
                  --arg on "$OBJECT_NAME" \
                  --arg tl "$TARGET_LOCATION" \
                  '{bucketname: $bn, objectname: $on, targetlocation: $tl}' )

Conditionally create json object

You can write

client.post("/workout", {
    userId: id,
    title: title,
    description: desc,
});

there's no need for the check. If desc is undefined the key description will be removed when stringified to JSON.

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