README

JSON Rule Engine

What does it do?

Pass a Rule and Data to engine and get a synchronous response on whether the Data satisfies the Rules.

@aipeel/json-rules-engine

Installation

    npm install @aipeel/json-rules-engine

Usage

Step 1: Define Rules JSON

Rules JSON must be an object

Must start with AND or OR which takes array of rule

Single Rule Criteria

{
    AND: [ Criteria1 ]
}

Multiple Rule Criteria --> Criteria 1 and 2 must be satisfied

{
    AND: [ Criteria1, Criteria2 .. ]
}

Multiple Levels of Rules --> Criteria 1 & 2 must be satisfied and either Criteria3 or Criteria4 must be satisfied

{
    AND: [
            {
                AND: [ Criteria1, Criteria2 ...]
            },
            {
                OR: [Criteria3, Criteria4 ..]
            }
        ]
}

Each Criteria must be an object

The key in criteria is an operator and value defines the metadata required for the operator to work

Examples of Criteria

{ 
    "between": { 
                    "min": "10", 
                    "max": "20", 
                    "attribute": "discount" 
                }
}

{ 
    "in": { 
            "value": ["C","Javascript","Python"], 
            "attribute": "lang"
        }
}

List of all criteria given below

Operator	Operator Property	Description	Example
between	min, max, attribute	Check if the property mentioned in attribute has value between min and max	`{ "between" : { "min" : "10" , "max" : "20" , "attribute" : "discount" }}`
lessThan	value, attribute	Check if the property mentioned in attribute has number less than value	`{ "lessThan" : { "value" : "80" , "attribute" : "price" } }`
lessThanEqual	value, attribute	Check if the property mentioned in attribute has number less than or equal value	`{ "lessThanEqual" : { "value" : "80" , "attribute" : "price" } }`
greaterThan	value, attribute	Check if the property mentioned in attribute has number greater than value	`{ "greaterThan" : { "value" : "80" , "attribute" : "price" } }`
greaterThanEqual	value, attribute	Check if the property mentioned in attribute has number greater than or equal value	`{ "greaterThanEqual" : { "value" : "80" , "attribute" : "price" } }`
equal	value, attribute	Check if the property mentioned in attribute has value equal to value provided	`{ "equal" : { "value" : "80" , "attribute" : "price" } }`
contains	value, attribute	Check if the property mentioned in attribute contains the value given.	`{ "contains" : { "value" : "great" , "attribute" : "desc" }}`
in	value, attribute	Check if the property mentioned in attribute is available in value array provided.	`{ "in" : { "value" : [ "C" , "Javascript" , "Python" ], "attribute" : "lang" }}`

A Rules JSON could be defined as

{ 
    "AND": [
        { "lessThan": {"value": "80", "attribute": "price"} },
        { "greaterThanEqual": {"value": "20", "attribute": "price"} },
        { "between": { "min": "10", "max": "20", "attribute": "discount" }}
    ]
}

{
    "OR":[
        { "contains": { "value": "great", "attribute": "desc" }},
        { "contains": { "value": "works", "attribute": "features"}},
        { "in": { "value": ["C","Javascript","Python"], "attribute": "lang"}},
    ]
}

Rules can be recursively nested as shown below

{
    "AND": [
            { 
                "AND": [
                    { "lessThan": {"value": "80", "attribute": "price"} },
                    { "greaterThanEqual": {"value": "20", "attribute": "price"} },
                    { "between": { "min": "10", "max": "20", "attribute": "discount" }}
                ]
            },
            {
                "OR":[
                    { "contains": { "value": "great", "attribute": "desc" }},
                    { "contains": { "value": "works", "attribute": "features"}},
                    { "in": { "value": ["C","Javascript","Python"], "attribute": "lang"}},
                ]
            }
        ]
}

Step2: Pass Data JSON and Rule JSON to Engine

    const Engine = require("@aipeel/json-rules-engine")

    Engine.apply(data,rule) // returns boolean - true or false

Complete end-to-end example below for reference

const Engine = require("@aipeel/json-rules-engine")

const rule = {
                    "AND": [
                            { 
                                "AND": [
                                    { "lessThan": {"value": "80", "attribute": "price"} },
                                    { "greaterThanEqual": {"value": "20", "attribute": "price"} },
                                    { "between": { "min": "10", "max": "20", "attribute": "discount" }}
                                ]
                            },
                            {
                                "OR":[
                                    { "contains": { "value": "great", "attribute": "desc" }},
                                    { "contains": { "value": "works", "attribute": "features"}},
                                    { "in": { "value": ["C","Javascript","Python"], "attribute": "lang"}},
                                ]
                            }
                        ]
                    }

let data = {
    id: 'ID1001',
    price: 50,
    discount: 10,
    desc: "This is a great product for developers",
    features: ["No Dependencies", "Open to Extension", "Synchronous", "works"],
    tags: ["json", "rule", "engine"],
    lang: "Javascript"
}

// example 1
console.log(`Does the data conform to rule? --> ${Engine.apply(data,rule)?"Yes":"No"}`);

//example 2
data.price = 100;
console.log(`Does the data conform to rule? --> ${Engine.apply(data,rule)?"Yes":"No"}`);

//example 3
data.price = 50;
data.discount = 21;
console.log(`Does the data conform to rule? --> ${Engine.apply(data,rule)?"Yes":"No"}`);

Output

Does the data conform to rule? --> Yes
Does the data conform to rule? --> No
Does the data conform to rule? --> No

Usage no npm install needed!