add rule result example

Author: Cache Hamm

examples/09-rule-results.js

@@ -0,0 +1,94 @@
+'use strict'
+
+/*
+ * This is a basic example demonstrating how to leverage the metadata supplied by rule results
+ *
+ * Usage:
+ * node ./examples/09-rule-results.js
+ *
+ * For detailed output:
+ * DEBUG=json-rules-engine node ./examples/09-rule-results.js
+ */
+require('colors')
+let Engine = require('../dist').Engine
+
+/**
+ * Setup a new engine
+ */
+let engine = new Engine()
+
+// rule for determining honor role student atheletes (student has GPA >= 3.5 AND is an athlete)
+engine.addRule({
+ conditions: {
+ all: [{
+ fact: 'athlete',
+ operator: 'equal',
+ value: true
+ }, {
+ fact: 'GPA',
+ operator: 'greaterThanInclusive',
+ value: 3.5
+ }]
+ },
+ event: { // define the event to fire when the conditions evaluate truthy
+ type: 'honor-roll',
+ params: {
+ message: 'Student made the athletics honor-roll'
+ }
+ }
+})
+
+function render (message, ruleResult) {
+ // if rule succeeded, render success message
+ if (ruleResult.result) {
+ return console.log(`${message}`.green)
+ }
+ // if rule failed, iterate over each failed condition to determine why the student didn't qualify for athletics honor roll
+ let detail = ruleResult.conditions.all.filter(condition => !condition.result)
+ .map(condition => {
+ switch (condition.operator) {
+ case 'equal':
+ return `was not an ${condition.fact}`
+ case 'greaterThanInclusive':
+ return `${condition.fact} of ${condition.factResult} was too low`
+ }
+ }).join(' and ')
+ console.log(`${message} ${detail}`.red)
+}
+
+/**
+ * On success, retrieve the student's username for display purposes, and render
+ */
+engine.on('success', (event, almanac, ruleResult) => {
+ almanac.factValue('username').then(username => {
+ render(`${username.bold} succeeded! ${event.params.message}`, ruleResult)
+ })
+})
+
+/**
+ * On failure, retrieve the student's username for display purposes, and render
+ */
+engine.on('failure', (event, almanac, ruleResult) => {
+ almanac.factValue('username').then(username => {
+ render(`${username.bold} failed - `, ruleResult)
+ })
+})
+
+// Run the engine for 5 different students
+Promise.all([
+ engine.run({ athlete: false, GPA: 3.9, username: 'joe' }),
+ engine.run({ athlete: true, GPA: 3.5, username: 'larry' }),
+ engine.run({ athlete: false, GPA: 3.1, username: 'jane' }),
+ engine.run({ athlete: true, GPA: 4.0, username: 'janet' }),
+ engine.run({ athlete: true, GPA: 1.1, username: 'sarah' })
+])
+
+/*
+ * OUTPUT:
+ *
+ * joe failed - was not an athlete
+ * larry succeeded! Student made the athletics honor-roll
+ * jane failed - was not an athlete and GPA of 3.1 was too low
+ * janet succeeded! Student made the athletics honor-roll
+ * sarah failed - GPA of 1.1 was too low
+ */