Blueprints scripting

Blueprint Visual Scripting is a powerfull scripting system based on the concept of using a node-based interface. This system is extremely flexible and powerful as it provides the ability to use virtually the full range of concepts and tools generally only available to programmers.

@bluepjs was inspired by the Epic Games Unreal Engine Blueprint System.


@bluepjs is a pseudo-typed scripting language. @bluepjs VM running in Java Script which is dynamic-typed, so all “Blueprint code” runing in VM really is dynamic typed. Dynamic types in Java Script is double-sided question - on one side it gives to developer fast and simple code development, and on other - it it may surprise developer on automatic types convering.

Blueprint concept is fixed typed and @bluepjs IDE fully implements this concept because it works great here:

  • different types have different colors what helps visually difference them

  • IDE block Edge connection when User try connect type-incompatible Slots.

@bluepjs has base set of types, but it can be extended same in programmatic way with Modules, same with types defined with IDE

Base Types


Boolean type - yes/no, 1/0, true/false, on/off


Integer numbers - 0, -100, 44, …


Float numbers - 1.23, -3.987, …


Strings - “Hello world!”, “Abc de fg”, …


Date and time.


Date only


Time only


Java Script object

Special Types


This is special type to define Execution Flow


Special type for Nodes which may work with different types

@bluepjs Types


Base type for Enums


Base type for Structs


Base type for Functions (!Not implemented currently)


Base type for Classes


Base type for Blueprint Objects (!Not implemented currently)

User defined types

When User creates enums, structs or classes in Libraries - new types appear in type selectors and nodes for this types are auto-generated by IDE.

Libraries Content

By default each VM doesn’t contains any Blueprints - they all are stored in Librararies.

Each Library contains user defined types and functions.

Each element in Libraries has code which should be unique inside Libraries.


UUID v4 is used to generate elements codes.

Library selector located at top bar on the left.

Library widget

Modules content

Modules also may provide additional enums, structs and classes for Vm. This content, defined inside Modules can’t be changed or removed by User.


Default library with code default is always exists, used and can’t be removed.

Each Library may include enums, structs, functions and classes.


Currently, there is only single library “default”.

This will be updated later

Library content panel allows see and manage Library content.

Library content panel

To create new element in Library - use selector on the header of Library content panel.

Add content to library


Enum is a dictionary with predefined values.


Enum example


Struct is a union of different data types into new “complex” type.


Struct example

Example “Demo struct” contains 2 fields:

  • field named Number field with code fieldNum type of basic/number

  • field named String field with code fieldStr type of basic/string


code for struct fields are defined by User.

It’s required for converting JavaScript objects into @bluep struct and back.


Speacking simple - Class is “upgraded” struct with functions.

Classes concept is part of Object Oriented Programming.

@bluepjs supports next OOP concepts:

  • Encapsulation

  • Inheritance - classes may extends other classes. Multi-inheritance is supported.

  • Polymorphism - Vm will control overriden methods and choose correct.

  • Properties and methods access control - public/private/protected

  • Constructors - @bluepjs supports only constructors - not destructors.

  • this concept (getter node)

Example of empty class:

Class builder example


This documentation doesn’t has a goal to describe OOP by itself. If you don’t know OOP - you should learn it by yourself.

You can use @bluepjs without OOP knowledges.


Functions are special Library executable entities.

Enums, struct and classes describe data types (simple or complex) - and functions can be executed by Vm.

There are next types of functions in @bluepjs:

  • Simple functions - can be executed by Vm on User request (by clicking “Run” button). Also they can be used in other functions as Node. Inputs and Outputs for function are defined by User using IDE

  • Event functions - executed automatically by Vm when corresponding event happens. Events can be provided by Modules and Actors. Event Inputs are defined by Developer (of Module/Actor). Events has no Outputs.

  • Class Constructors - executed by Vm when object of class is created. IDE automatically generates required Nodes.

  • Class Methods - executed by Vm when corresponding method is called. IDE automatically generates required Nodes.

For defining Function behavior - Blueprint editor is used.

Example of function blueprint:

Function blueprint example

Execution Flow in Depth

Execution flow defined by connecting Execution Outputs and Execution Inputs of different Execution Nodes what creates Execution Edge.

Function blueprint execution flow simple

On example image Execution Nodes are 1, 2 and 3, and Execution Edges are a, b and c.

Execution Context

For each Blueprint execution Vm generates closed “sandbox” where all data of execution is stored. This “sandbox” in @bluepjs named Execution Context.

Context exists while Bluprint is executed by Vm and destroyed on execution complete.

Context is hidden from User but accessible for Developer.

For methods and constructors types of functions special this entity exists for context pointing to object of class.

Call Node

Blueprint Execution starts from special Call Node. It can be only one Call Node per Blueprint.

Outputs of Call Node are auto-defined by Function inputs.

Example of Call Node for function without Inputs:

Call Node example

Return Node

Execution follows to Execution Edges of Nodes until there are Execution Edges.

If Function has Outputs - special Return Node should be used to set them.

Example of Call Node for function with sing Output of type basic/string named “outputs 0”:

Return Node example

If Return Node is not connected to Execution flow - function outputs are undefined.

Modifiers and Getters Nodes execution

When Node executes - it sets it’s Outputs, so when Node is executed - Execution Context contains output data.

Before Vm executes any Node it prepares Node Inputs. If Input slot of Node is connected to other Node - Vm will execute it automatically, to prepare required Inputs.


Execution flow in depth

Full Execution Flow for Blueprint is next:

  1. Call Node (1) is executed, set it’s “now” output to Context

  2. Vm checks Execution Edge (a) and found next Node to execute (2)

  3. Vm prepares Node Inputs and found that Input slot “Message” is connected to Output of Node “String Append” (2a).

  4. Vm prepares 2a to execute and found that first Input Slot is defined manualy, but second Input slot connected with another Node (2b)

  5. Vm prepares 2b to execute and found that first Input Slot is defined manualy and second Input Slot connected to Node with defined (in Context) Output.

  6. Because all inputs for 2b are ready - 2b node is executed and set its output

  7. Because now all inputs for 2a are ready - 2a is executed and set its output

  8. Because now all inputs for 2 are ready - 2 is executed and set its outputs

  9. Vm checks Execution Edge b and found Node 3.

  10. Preparing Node 3 to execute - Vm found no Node Inputs so Node is executing set its outputs

  11. Vm checks Execution Edge c and found Node 4.. and so on

Main difference between Execution Nodes and Modifier/Getter Nodes is that Modifiers/Getters Nodes are executed every time when theirs Outputs are required, and Execution Nodes are executed only according to Execution Edges.