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    js-feel

    1.4.7¬†‚Äʬ†Public¬†‚Äʬ†Published

    Build Status Coverage Status License: MIT npm

    NPM

    About

    FEEL is an expression language based on DMN specification conformance level 3. Written using PEG.js - JavaScript Parser Generator. FEEL is a very powerful language built with the purpose of defining rules in Business Rule Engines. FEEL also offers an API to implement and execute Decision Table defined in excel (.xlsx)

    Getting Started

    FEEL is a completely flexible library which can be used with any project to add support for Decision Table. It also comes with a powerful expression language termed FEEL built-in to define a multitude of decision rules.

    Installation

    Development

    # npm install 
    npm install js-feel --save
     

    Contribution

    # clone repo 
    git clone https://github.com/EdgeVerve/feel.git
     
    # or fork repo 
     
    # install dependencies 
    npm install
     
    # run test cases 
    npm test
     
    # watch for changes in source and grammar 
    gulp watch
     
    # generate parser from grammar 
    gulp generate
     
    # lint source files 
    npm run lint
     
    # lint-fix source files 
    npm run lintfix

    Usage

    Using Decision Table

    Decision tables are defined in excel (.xlsx). Please check Sample Rules. Each cell in the body of the decision table has to be a valid FEEL expression. The following make use of FEEL parser to parse and execute expressions and hence the decision logic.

    Excel to Decision Table

    const { decisionTable } = require('feel')();
     
    const csv = decisionTable.xls_to_csv('./test/StudentFinancialPackageEligibility.xlsx');
    const decision_table = decisionTable.csv_to_decision_table(csv[0]);

    Execute Decision Table

    The Decision Table (decision_table) created in the previous step can be executed using; decisionTable.execute_decision_table

     
    const payload = {"Student GPA" : 3.6,"Student Extra-Curricular Activities Count" : 4,"Student National Honor Society Membership" : "Yes"};
    decisionTable.execute_decision_table("StudentFinancialPackageEligibility", decision_table,payload, (results)=> {
        console.log(results)
    });

    Using FEEL Standalone

    const {feel} = require('feel')();
     
    const rule = 'a + b - c';
    const context = {
        a: 10,
        b: 20,
        c: 5
    };
     
    const parsedGrammar = feel.parse(rule);
    parsedGrammar.build(context).then(result => {
        console.log(result);
    }).catch(err => console.error(err));

    Sample FEEL Expressions

    Some valid FEEL expressions (logically categorized):

    Arithmetic

    • a + b - c
    • ((a + b)/c - (d + e*2))**f
    • 1-(1+rate/12)**-term
    • (a + b)**-c
    • date("2012-12-25") + date("2012-12-24")
    • time("T13:10:06") - time("T13:10:05")
    • date and time("2012-12-24T23:59:00") + duration("P1Y")

    Comparision

    • 5 in (<= 5)
    • 5 in ((5..10])
    • 5 in ([5..10])
    • 5 in (4,5,6)
    • 5 in (<5,>5)
    • (a + 5) >= (7 + g)
    • (a+b) between (c + d) and (e - f)
    • date("2012-12-25") > date("2012-12-24")
    • date and time("2012-12-24T23:59:00") < date and time("2012-12-25T00:00:00")

    Conjunction

    • a or b
    • a and b
    • ((a or b) and (b or c)) or (a and d)
    • ((a > b) and (a > c)) and (b > c)
    • ((a + b) > (c - d)) and (a > b)
    • a or b or a > b
    • (x(i, j) = y) and (a > b)
    • (a + b) > (c - d) and (a > b)

    For

    • for a in [1,2,3] return a * a
    • for age in [18..40], name in ["george", "mike", "bob"] return status

    Function Definition

    • function(age) age < 21
    • function(rate, term, amount) (amount*rate/12)/(1-(1+rate/12)**-term)

    If

    • if applicant.maritalStatus in ("M", "S") then "valid" else "not valid"
    • if Pre-Bureau Risk Category = "DECLINE" or Installment Affordable = false or Age < 18 or Monthly Income < 100 then "INELIGIBLE" else "ELIGIBLE"
    • if "Pre-Bureau Risk Category" = "DECLINE" or "Installment Affordable" = false or Age < 18 or "Monthly Income" < 100 then "INELIGIBLE" else "ELIGIBLE"

    Quantified

    • some ch in credit history satisfies ch.event = "bankruptcy"

    Date Time Semantics

    • time("13:10:05@Etc/UTC").hour
    • time("13:10:05@Etc/UTC").minute
    • time("13:01:05+05:30").second
    • date and time("2012-12-24T23:59:00").year
    • date("2017-06-10").month
    • date("2017-06-10").day
    • duration("P13M").years
    • duration("P1Y11M").months
    • duration("P5DT12H10M").days
    • duration("P5DT12H10M").hours
    • duration("P5DT12H10M").minutes
    • duration("P5DT12H10M25S").seconds

    Date Time Conversion and Equality

    • date("2012-12-25") ‚Äď date("2012-12-24") = duration("P1D")
    • date and time("2012-12-24T23:59:00") + duration("PT1M") = date and time("2012-12-25T00:00:00")
    • time("23:59:00z") + duration("PT2M") = time("00:01:00@Etc/UTC")
    • date and time("2012-12-24T23:59:00") - date and time("2012-12-22T03:45:00") = duration("P2DT20H14M")
    • duration("P2Y2M") = duration("P26M")

    Please note: This is not a complete list of FEEL Expressions. Please refer DMN Specification Document for detailed documentation on FEEL grammar.

    Sample Rules

    Validation.xlsx

    PostBureauRiskCategory.xlsx

    ElectricityBill.xlsx

    Reference

    For comprehensive set of documentation on DMN, you can refer to :

    DMN Specification Document

    Install

    npm i js-feel

    DownloadsWeekly Downloads

    254

    Version

    1.4.7

    License

    none

    Unpacked Size

    637 kB

    Total Files

    38

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