BizRez Rules - JavaScript Condition Event Engine

A small functional Rule Engine - simple maybe an understatement...

Intro

Simplicity is elegance. This rule engine is NOT forward chaining, backward chaining, nor is this an inference engine. What it is, is a pragmatic reactive engine. Simply stated, when there is a condition, execute an action -- most assuredly in a stateless manner.

Prime directives, and ables ...

• Stateless
• Simple input, output, and process
• Asynchronous non-blocking invocations
• Rules to be self contained and serializable to a database (persistable)
• Rules to be versioned (versionable)
• Rules to be inventoried and stored in a library (sharable)
• Rules can be modified on-the-fly (adaptable)
• Rules can be unit tested independently (testable)
• Crazy fast

#####Martin Fowler on Rule Engines

// Rule Abilities 
{ables: [persistable, versionable, shareable, adaptable, testable, chainable, reusable, extensible]}

Dependencies

• Underscore.js for Mapreduce Decision Tables
• Async.js for asynchronous hooks and behavior
• Mocha.js for for test infecting the code (good infection)
• Require.js for the module loader

A few Use Cases for Usage

• Validations
• Mappings
• Calculations
• Batch processing
• Automated business rules - decision engine
• Automation of sequential events and process
• Home security, sprinkler systems, and darn maybe your car...

Benefits

• Repository of rules
• Traceability
• Modify the rule not the code
• Dynamic changeability - conditions change so do the execution
• Easy to understand and modify
• Extensible
• Maintainable
• Reusable
• Chainable
• Micro foot print and scalable

Design - IPO (Input Process Output)

// Input - Example Greetings

facts = {
          input: { hour: 10 },
          output: {greeting:''}
         }

// Process - Example Decision Table
rule =  {

                "id": "GREETING",
                "description": "Show correct greeting based on time",
                "condition": function (facts) {
                    // We will calculate the results regardless
                    return true;
                },
                "action": function (facts) {

                    var decisionTable
                        = [
                        {from: 0, to: 11, greeting: 'Good Morning'},
                        {from: 12, to: 17, greeting: 'Good Afternoon'},
                        {from: 18, to: 22, greetings: 'Good Evening'},
                        {from: 23, to: 24, greetings: 'Good Night'}
                    ];

                    var resultArray;

                    // MAP
                    resultArray = _.map(decisionTable, function (row) {
                        var result = "";
                        if (facts.input.hour >= row.from && facts.input.hour <= row.to) {
                            result = row.greeting;
                        }
                        return result;
                    });
                    // Reduce
                    var result = _.reduce(resultArray, function (memory, element) {
                        if (element !== "") {
                            memory = element;
                        }
                        return  memory;
                    });
                    facts.output.greeting = result;

                }
            }
// Output - Example result

facts = {
          input: { hour: 10 },
          output: {greeting:'Good Morning'}
         }

Download

The source is available for download from GitHub.

Alternatively, you can install using Node Package Manager npm:

npm install rulesengine

mocha test