Node-rules is a forward chaining Rules Engine, written on node.js.

install this via

npm install node-rules 

Node-rules takes rules written in JSON format as input. These rules get applied on the specified iputs(facts) to the rule engine.

A Rules consist of

1. name - the name for the rule

2. conditions - a function which takes inputs and upon returning its results the rule engine executes the corresponding consequence.

3. consequence - a function which gets executed accoring to the return value from a condititon after executed.

4. description - the description for the rule

5. priority - number which decides the order at which the rule gets applied on the supplied facts.

6. on - boolean telling whether or not the rule should be considered by the rule engine.

{"name": "transaction minimum", "description": "blocks transactions below value x", "priority": 3, "on":1, "condition": function(fact,cb){cb(fact && (fact.transactionTotal < 500))}, "consequence": function(cb){console.log("Rule 1 matched for "+this.name+": blocks transactions below value 500. Rejecting payment."); this.result = false; this.process = true; cb()} } 

Facts are those input json values on which the rule engine applies its rule to obtain results. A fact can have multiple attributes.

{"userIP": "27.3.4.5", "name":"user4", "eventRiskFactor":8, "userCredibility":2, "application":"MOB2", "userLoggedIn":true, "transactionTotal":400, "cardType":"Credit Card", "cardIssuer":"VISA", } 

##Usage

The example below shows how to use the rule engine to apply a sample rule on a specific fact.

varRuleEngine=require('node-rules');varrules=[{"name": "transaction minimum","description": "blocks transactions below value x","priority": 3,"on":1,"condition": function(fact,cb){cb(fact&&(fact.transactionTotal<500));},"consequence": function(cb){console.log("Rule 1 matched for "+this.name+": blocks transactions below value 500. Rejecting payment.");this.result=false;this.process=true;cb();}}];varfact={"userIP": "27.3.4.5","name":"user4","eventRiskFactor":8,"userCredibility":2,"application":"MOB2","userLoggedIn":true,"transactionTotal":400,"cardType":"Credit Card","cardIssuer":"VISA",};varR=newRuleEngine(rules);R.execute(fact,function(result){if(result.result)console.log("\n-----Payment Accepted for----\n");elseconsole.log("\n-----Payment Rejected for----\n");console.log(result);});

Both the rules and the facts used in this module are based on the node module jools. Its a modified version of jools with a non blocking version of applying the rule engine on the facts. The rule engine logic was been modified sothat the rule executions on separate facts donot block each other.