decision_table

decision_table

Simple implementation of Decision Tables (https://en.wikipedia.org/wiki/Decision_table).

Installation

For Node.JS or bundlers (Wepback, Browserify):

# By NPM
npm i decision_table --save
# By Yarn
yarn add decision_table --save

For browser (compressed library at file lib/decision-table.js):

<!-- Development environment version -->
<script src="path/to/decision-table.dev.js"></script>
<!-- Production environment version -->
<script src="path/to/decision-table.prod.js"></script>

Usage

Importing

For Node.JS or bundlers you just need to import DecisionTable class:

const {DecisionTable} = require('decision-table');
// or
import {DecisionTable} from 'decision-table';

In browsers you can get it from global variable:

window.dt.DecisionTable;

Environment

Library uses standard Node.JS environment variable (NODE_ENV). In development mode (NODE_ENV !== 'production') library runs some tests for each adding action and condition.

Browser versions of library has defined environment:

• lib/decision-table.dev.js - development environment (all test running always, not compressed);
• lib/decision-table.prod.js - development environment (all test running always, compressed);

API

new DecisionTable()

Creates new instance of Decision Table. No arguments.

Example:

var table = new window.dt.DecisionTable();

DecisionTable.noConflict()

Static method which returns Decision Table constructor and returns a previous value of window.dt field.

Example:

window.mynamespace.DecisionTable = window.dt.DecisionTable.noConflict();
console.log(window.dt); // Must be a previous value now

In Node.JS this method just returns Decision Table constructor.

DecisionTable.testAction(action)

Special static method which provides simple testing for your actions. In "development" environment this method will be run for each adding action.

DecisionTable.testCondition(name, func)

Special static method which provides simple testing for your conditions. In development environment this method will be run for each adding condition.

DecisionTable.prototype.addCondition(name, func)

Instance method which adds new condition to table. If condition with this name was already added it will be overriden.

Arguments:

• name - string identifier of condition;
• func - condition function, must have no arguments and return a boolean value;

Example:

var A = true, B = false;
table.addCondition('A', function() { return A; });
table.addCondition('B', function() { return B; });

DecisionTable.prototype.removeCondition(name)

Removes condition from table. For any actions which requires condition with this name it will be automaticaly equals "false".

table.removeCondition('A');
table.removeCondition('B');

DecisionTable.prototype.addAction(action)

Adds new action to table. Argument action must be an object which contains fields:

• whenTrue - array of conditions names which must be a "true" to do action;
• whenFalse - array of conditions names which must be a "false" to do action;
• execute - action's body, code to execute on this action.

If whenTrue or whenFalse will be both not defined or empty, action will never be executed.

If one of actions in whenTrue or whenFalse is not defined in table (or removed from it), action will never be executed.

Example:

table.addAction({
    whenTrue: ['A'],
    execute: function() {
        console.log('Executed only if A is true');
    }
});
table.addAction({
    whenFalse: ['A'],
    execute: function() {
        console.log('Executed only if A is false');
    }
});
table.addAction({
    whenTrue: ['B'],
    execute: function() {
        console.log('Executed only if B is true');
    }
});
table.addAction({
    whenFalse: ['B'],
    execute: function() {
        console.log('Executed only if B is false');
    }
});
table.addAction({
    whenTrue: ['A', 'B'],
    execute: function() {
        console.log('Executed only if A and B are true');
    }
});
table.addAction({
    whenFalse: ['A', 'B'],
    execute: function() {
        console.log('Executed only if A and B are false');
    }
});
table.addAction({
    whenTrue: ['A'],
    whenFalse: ['B'],
    execute: function() {
        console.log('Executed only if A is true and B is false');
    }
});
table.addAction({
    whenTrue: ['B'],
    whenFalse: ['A'],
    execute: function() {
        console.log('Executed only if B is true and A is false');
    }
});

DecisionTable.prototype.removeAction(action)

Removes action from table. Please note, that this method just equals pointes to objects.

DecisionTable.prototype.run();

Check all conditions and execute all approved actions.

Example:

table.run();

Full example (for browser)

var table = new window.dt.DecisionTable();
var A, B;

table.addCondition('A', function() { return A; });
table.addCondition('B', function() { return B; });

table.addAction({
    whenTrue: ['A'],
    execute: function() {
        console.log('Executed only if A is true');
    }
});
table.addAction({
    whenFalse: ['A'],
    execute: function() {
        console.log('Executed only if A is false');
    }
});
table.addAction({
    whenTrue: ['B'],
    execute: function() {
        console.log('Executed only if B is true');
    }
});
table.addAction({
    whenFalse: ['B'],
    execute: function() {
        console.log('Executed only if B is false');
    }
});
table.addAction({
    whenTrue: ['A', 'B'],
    execute: function() {
        console.log('Executed only if A and B are true');
    }
});
table.addAction({
    whenFalse: ['A', 'B'],
    execute: function() {
        console.log('Executed only if A and B are false');
    }
});
table.addAction({
    whenTrue: ['A'],
    whenFalse: ['B'],
    execute: function() {
        console.log('Executed only if A is true and B is false');
    }
});
table.addAction({
    whenTrue: ['B'],
    whenFalse: ['A'],
    execute: function() {
        console.log('Executed only if B is true and A is false');
    }
});

A = true;
B = true;
table.run();

A = false;
B = true;
table.run();

A = true;
B = false;
table.run();

A = false;
B = false;
table.run();

Roadmap

• Version 0.5.0 - optional conditions ("OR" logic);
• Version 0.9.0 - asynchronous conditions;