---
url: >-
  /statelake/scripting-reference/json-for-scripts/json-object-classes-and-variable-types.md
---

# JSON Object Classes & Variable Types

## JSON Object Classes

The advantage of encoding data into a relatively plain string text format of characters such as JSON, is that it can be passed easily between a web browser and web server, or can be read from or saved to a text file on disk, making it an ideal data‑interchange language.

As detailed below, specific characters such as square brackets \[ and ], and curly braces { and }, are used to mark the structural aspects within the string.

The fundamental data element in JSON is a name/value pair (or key/value pair or property).

* A JSON structure is built from JSON objects. An object is an unordered set of name/value pairs, starting with a left curly brace { and ending with a right curly brace }.
* The JSON name (key) and value are separated by a colon : and each set of pairs is separated by a comma.
* The name of the JSON item is always in the left side of the colon.
* A JSON **Array** is an ordered collection of values, beginning with a left square bracket \[, and ending with a right square bracket ].
* Values are separated by commas.

Each Object or Array can contain a combination of Objects, Arrays, name/value pairs, and/or simple data values (e.g. a string in double quotes such as **AbC**, a number, true or false or null, an object or an array), to any required depth of nesting.

Further details can be found at <http://www.json.org> and elsewhere.

There are 7 pre-defined classes available to deal with JSON entities:

* **TJSONValue** – The base class of all the JSON classes used to store parsed JSON data. The rest of the JSON related classes are inherited from **TJSONValue**. Any of the JSON entities can be treated as **TJSONValue**, for example, can be serialized into a string.
* **TJSONObject** – Represents a JSON object. It holds a set of paired keys (strings) and values (**TJSONValue**), and provides an easy-to-use interface to access and modify them. Also referred to as name/value pairs or properties.
* **TJSONArray** – Represents a JSON array. It keeps an array of enclosed **TJSONValue** values, and can include unnamed objects.
* **TJSONString, TJSONNumber, TJSONBool, TJSONNull** – Represents string, number, boolean and null values respectively.

**Remember**: JSON objects and arrays are always passed by reference as regular objects in Statelake script. When you modify an object or array by using a variable (reference), you actually modify the original object or array that the variable refers to.

## JSON Variable Types

Every JSON value can be tested for a specific type, by either using the **is** operator, or one of the following functions:

* IsString
* IsInt
* IsInt64
* IsNumber
* IsBoolean
* IsObject
* IsArray

Sample code -

```pascal
if object['str'].IsString then
    LogInfo('str field is a string');
if object['str'] is TJSONString then
    LogInfo('str field is a string');

if object['number’].IsNumber then
    LogInfo(‘number field is a number’);
if object['number] is TJSONNumber then
    LogInfo(‘number field is a number’);

if jsonValue.IsObject then
    LogInfo('jsonValue is an object');
if jsonValue is TJSONObject then
    LogInfo('jsonValue is an object');
```