PratJS

Prat is a dialog system. PratJS is an interpreter of Prat, for the web.

Installation

npm i pratjs

Syntax highlighting

Prat is the official VSCode extension for Prat.

Demos

• magne.dev/chat

Basic usage

import { Prat } from 'pratjs';

const pratString = `
Hello, this is Prat!
\tHey, Prat!
\t\tIt's nice to meet you.
\tWhat is Prat?
\t\tPrat is a dialog system with some cool features.
`;

const prat = Prat.fromString(pratString);

prat.get();
/*
{
  statement: 'Hello, this is Prat!'
  responses: ['Hey, Prat!', 'What is Prat?']
  author: ''
}
*/
prat.print();
/*
Hello, this is Prat!
  (0) Hey, Prat!
  (1) What is Prat?
*/
prat.respond(1);
prat.print();
/*
Prat is a dialog system with some cool features.
*/

More examples may be seen below or in the tests.

API

class Prat {
  constructor(lines: PratLine[]);
  static fromString(pratString: string): Prat;
  get(): {
    statement: string;
    responses: string[];
    author: string;
  };
  getFromKey(key: string): {
    statement: string;
    responses: string[];
    author: string;
  };
  print(callback?: (result: string) => void): Prat;
  respond(responseIndex?: string | number): Prat;
  pushLine(line: PratLine): Prat;
  onEnd(callback: () => void): Prat;
  hasEnded(): boolean;
  resetContext(): Prat;
}

Prat docs

A Prat consists of statements and responses. A statement may lead to multiple selectable responses, but a response may only lead to one statement. An even number of tabs indicates a statement, and an odd number of tabs indicates a response.

This is a statement.
	This is a response.
		This statement will follow the first response.
	This is another response.
		This statement will follow the second response.
This statement will follow regardless of what response was selected.

Extensions

Any line may be extended by the following extensions. They are all on the form <symbol>{<content>}. The placement of an extension within a line does not matter (except for insertions). However, the convention is to place key and author symbols at the beginning and the rest at the end.

class PratSymbol {
  key = '#';
  goto = '>';
  author = '@';
  prepare = '!!';
  action = '!';
  condition = '?';
  insert = '$';
  comment = '%';
  inherit = '+';
  left = '{';
  right = '}';
}

Key: #{key}

By default, all lines are are assigned #<line number> as their key. This may be overridden with the key symbol.

#{main} The key of this line is 'main'

Goto: >{key}

By default, all lines lead to the following line. This may be changed with the goto symbol.

#{start}
This is an infinite loop.
>{start}

Author: @{author}

The author symbol is used to assign an author to the line. The author may be accessed with prat.get().author

@{Magne} The author of this line is 'Magne'

Prepare: !!{javascript}

The prepare symbol is used to run code at talk initialization. This is useful to initialize variables. $g indicates global context.

Let's initialize a global variable !!{$g.shouldSkipLine = true}

Action: !{javascript}

The action symbol is used to run code when a line is reached. This is useful to update variables.

Let's toggle this variable !{$g.shouldSkipLine = !$g.shouldSkipLine}

Condition: ?{javascript}

With the condition symbol, one may set conditions to when the line show be shown or skipped.

?{$g.shouldShowLine} This line is skipped if the local variable 'shouldShowLine' is false.

Insert: ${javascript}

With insertions, one may include dynamic content in a line.

!!{$g.age = '< 18'}
Are you over 18?
	Yes !{$g.age = '18+'}
	No
Your age is ${$g.age}.

Comment: %{comment}

This is part of the Prat %{but this will not be included.}

Inherit: +{key}

With the inherit symbol, a line may use extensions from another line. This is useful to prevent copying and pasting.

>{start}

%{Declarations}
#{showOnce} !!{$l.show = true} ?{$l.show} !{$l.show = false}

#{start}
Hello.
These lines will be shown in every loop.
But this line will only be shown in the first loop. +{showOnce}
These lines will be shown in every loop.
>{start}

Context

Variables should be assigned to global g or local l context. Global variables are accessible from the whole talk, while local variables are local to a single line. You may also access the Prat and PratLine instances from the talk with g.instance and l.instance, but this is highly experimental.