Real-World Scenarios - Rule Engine JS

E-commerce

Dynamic Pricing

Price rules based on user segments

Inventory Management

Stock alerts and reordering

Fraud Detection

Suspicious order patterns

Promotions

Coupon and discount logic

Dynamic Pricing

import { createRuleEngine, createRuleHelpers } from 'rule-engine-js';

const engine = createRuleEngine();
const rules = createRuleHelpers();

// VIP discount (20%)
const vipDiscount = rules.and(
  rules.eq('user.tier', 'vip'),
  rules.gte('user.loyaltyPoints', 1000)
);

// Bulk discount (15%)
const bulkDiscount = rules.and(
  rules.gte('cart.items.length', 10),
  rules.gte('cart.total', 500)
);

// First-time customer (10%)
const newCustomerDiscount = rules.and(
  rules.eq('user.orderCount', 0),
  rules.gte('cart.total', 50)
);

// Seasonal discount (25%)
const seasonalDiscount = rules.and(
  rules.in('product.category', ['winter-clothing', 'holiday-gifts']),
  rules.gte('currentMonth', 11) // November or December
);

function calculateDiscount(data) {
  if (engine.evaluateExpr(seasonalDiscount, data).success) {
    return 0.25;
  }
  if (engine.evaluateExpr(vipDiscount, data).success) {
    return 0.20;
  }
  if (engine.evaluateExpr(bulkDiscount, data).success) {
    return 0.15;
  }
  if (engine.evaluateExpr(newCustomerDiscount, data).success) {
    return 0.10;
  }
  return 0;
}

const order = {
  user: { tier: 'vip', loyaltyPoints: 1500, orderCount: 25 },
  cart: { items: [], total: 300 },
  product: { category: 'electronics' },
  currentMonth: 6
};

const discount = calculateDiscount(order);
const finalPrice = order.cart.total * (1 - discount);

console.log(`Discount: ${discount * 100}%`);
console.log(`Final price: $${finalPrice}`);
// Discount: 20%
// Final price: $240

Fraud Detection

import { StatefulRuleEngine } from 'rule-engine-js';

const baseEngine = createRuleEngine();
const statefulEngine = new StatefulRuleEngine(baseEngine);

const fraudRules = {
  'high-value-new-customer': rules.and(
    rules.lte('user.accountAge', 7), // Account less than 7 days old
    rules.gte('order.total', 1000),
    rules.eq('user.orderCount', 0)
  ),

  'rapid-orders': rules.and(
    rules.increased('user.orderCount'),
    rules.changedBy('user.orderCount', 5) // 5+ orders in short time
  ),

  'shipping-billing-mismatch': rules.and(
    rules.neq('shipping.country', 'billing.country'),
    rules.gte('order.total', 500)
  ),

  'unusual-location': rules.and(
    rules.changed('user.ipCountry'),
    rules.neq('user.ipCountry', 'user.registeredCountry')
  )
};

statefulEngine.on('triggered', (event) => {
  console.log(`🚨 Fraud alert: ${event.ruleId}`);
  console.log('Review order:', event.context.order.id);
  // Flag for manual review
  // Notify fraud team
  // Hold payment processing
});

const orderData = {
  user: {
    accountAge: 2,
    orderCount: 0,
    ipCountry: 'US',
    registeredCountry: 'US'
  },
  order: {
    id: 'ORD-123',
    total: 1500
  },
  shipping: { country: 'US' },
  billing: { country: 'US' }
};

// Evaluate all fraud rules
const results = statefulEngine.evaluateBatch(fraudRules, orderData);
// 🚨 Fraud alert: high-value-new-customer

Healthcare

Patient Monitoring

const patientAlerts = {
  'critical-vitals': rules.and(
    rules.or(
      rules.lte('vitals.heartRate', 40),
      rules.gte('vitals.heartRate', 120),
      rules.lte('vitals.bloodPressure.systolic', 90),
      rules.gte('vitals.bloodPressure.systolic', 180)
    )
  ),

  'deteriorating-condition': rules.and(
    rules.decreased('vitals.oxygenLevel'),
    rules.lte('vitals.oxygenLevel', 90)
  ),

  'medication-due': rules.and(
    rules.gte('currentTime', 'medication.nextDoseTime'),
    rules.eq('medication.administered', false)
  )
};

statefulEngine.on('triggered', (event) => {
  const alerts = {
    'critical-vitals': '🚨 CRITICAL: Immediate attention required',
    'deteriorating-condition': '⚠️ WARNING: Patient condition worsening',
    'medication-due': '💊 REMINDER: Medication due'
  };

  console.log(alerts[event.ruleId]);
  // Notify medical staff
  // Update patient dashboard
  // Log to medical records
});

const patientData = {
  vitals: {
    heartRate: 125,
    bloodPressure: { systolic: 140, diastolic: 90 },
    oxygenLevel: 95
  },
  medication: {
    nextDoseTime: '14:00',
    administered: false
  },
  currentTime: '14:30'
};

statefulEngine.evaluateBatch(patientAlerts, patientData);
// 🚨 CRITICAL: Immediate attention required
// 💊 REMINDER: Medication due

Financial Services

Transaction Monitoring

const transactionRules = {
  'large-transaction': rules.and(
    rules.gte('transaction.amount', 10000),
    rules.increased('transaction.amount')
  ),

  'rapid-withdrawals': rules.and(
    rules.increased('account.withdrawalCount'),
    rules.changedBy('account.withdrawalCount', 5),
    rules.gte('account.totalWithdrawn', 5000)
  ),

  'low-balance-warning': rules.and(
    rules.decreased('account.balance'),
    rules.lte('account.balance', 100),
    rules.gte('account.balance', 0)
  ),

  'overdraft': rules.and(
    rules.lt('account.balance', 0),
    rules.decreased('account.balance')
  ),

  'suspicious-pattern': rules.and(
    rules.changed('transaction.location'),
    rules.neq('transaction.location', 'account.usualLocation'),
    rules.gte('transaction.amount', 1000)
  )
};

statefulEngine.on('triggered', (event) => {
  const actions = {
    'large-transaction': () => {
      console.log('📧 Email verification sent');
      // Send 2FA code
    },
    'rapid-withdrawals': () => {
      console.log('🔒 Account temporarily locked');
      // Require additional verification
    },
    'low-balance-warning': () => {
      console.log('⚠️ Low balance notification');
      // SMS alert
    },
    'overdraft': () => {
      console.log('❌ Transaction blocked');
      // Block further transactions
    },
    'suspicious-pattern': () => {
      console.log('🚨 Fraud review initiated');
      // Flag for manual review
    }
  };

  actions[event.ruleId]?.();
});

let accountData = {
  account: {
    balance: 5000,
    withdrawalCount: 2,
    totalWithdrawn: 500,
    usualLocation: 'New York'
  },
  transaction: {
    amount: 15000,
    location: 'New York'
  }
};

statefulEngine.evaluateBatch(transactionRules, accountData);
// 📧 Email verification sent

IoT & Smart Home

Smart Thermostat

const thermostatRules = {
  'cooling-needed': rules.and(
    rules.gte('sensors.temperature', 'settings.maxTemp'),
    rules.increased('sensors.temperature'),
    rules.eq('hvac.mode', 'auto')
  ),

  'heating-needed': rules.and(
    rules.lte('sensors.temperature', 'settings.minTemp'),
    rules.decreased('sensors.temperature'),
    rules.eq('hvac.mode', 'auto')
  ),

  'away-mode': rules.and(
    rules.eq('sensors.motion', false),
    rules.gte('sensors.motionlessMinutes', 30),
    rules.eq('settings.ecoMode', true)
  ),

  'window-open': rules.and(
    rules.eq('sensors.windowOpen', true),
    rules.or(
      rules.eq('hvac.heating', true),
      rules.eq('hvac.cooling', true)
    )
  )
};

statefulEngine.on('triggered', (event) => {
  const actions = {
    'cooling-needed': () => {
      console.log('❄️ Cooling activated');
      // Turn on AC
    },
    'heating-needed': () => {
      console.log('🔥 Heating activated');
      // Turn on heat
    },
    'away-mode': () => {
      console.log('🌙 Eco mode activated');
      // Reduce energy usage
    },
    'window-open': () => {
      console.log('⚠️ Window open - HVAC paused');
      // Pause HVAC to save energy
    }
  };

  actions[event.ruleId]?.();
});

const homeData = {
  sensors: {
    temperature: 78,
    motion: true,
    motionlessMinutes: 0,
    windowOpen: false
  },
  settings: {
    maxTemp: 75,
    minTemp: 68,
    ecoMode: true
  },
  hvac: {
    mode: 'auto',
    heating: false,
    cooling: false
  }
};

statefulEngine.evaluateBatch(thermostatRules, homeData);
// ❄️ Cooling activated

Content Moderation

const moderationRules = {
  'spam-detection': rules.and(
    rules.contains('content.text', 'http'),
    rules.gte('content.linkCount', 3),
    rules.lte('user.accountAge', 7)
  ),

  'profanity-filter': rules.or(
    rules.contains('content.text', 'badword1'),
    rules.contains('content.text', 'badword2')
    // Add more as needed
  ),

  'rapid-posting': rules.and(
    rules.increased('user.postCount'),
    rules.changedBy('user.postCount', 10), // 10 posts in short time
    rules.lte('user.trustScore', 50)
  ),

  'mass-report': rules.and(
    rules.increased('content.reportCount'),
    rules.gte('content.reportCount', 5)
  )
};

statefulEngine.on('triggered', (event) => {
  const actions = {
    'spam-detection': () => {
      console.log('🚫 Post flagged as spam');
      // Hide post, notify moderators
    },
    'profanity-filter': () => {
      console.log('⚠️ Profanity detected');
      // Replace with asterisks or reject
    },
    'rapid-posting': () => {
      console.log('⏱️ Rate limit applied');
      // Slow down posting
    },
    'mass-report': () => {
      console.log('👁️ Content under review');
      // Escalate to human moderators
    }
  };

  actions[event.ruleId]?.();
});

const postData = {
  content: {
    text: 'Check out http://spam.com and http://scam.com!',
    linkCount: 2,
    reportCount: 0
  },
  user: {
    accountAge: 2,
    postCount: 15,
    trustScore: 30
  }
};

statefulEngine.evaluateBatch(moderationRules, postData);

SaaS Platform

Usage-Based Billing

const billingRules = {
  'usage-threshold-80': rules.and(
    rules.gte('usage.percentage', 80),
    rules.lt('usage.percentage', 100),
    rules.increased('usage.percentage')
  ),

  'usage-exceeded': rules.and(
    rules.gte('usage.percentage', 100),
    rules.increased('usage.percentage')
  ),

  'upgrade-recommended': rules.and(
    rules.gte('usage.percentage', 90),
    rules.eq('subscription.tier', 'basic'),
    rules.gte('subscription.consecutiveMonthsHigh', 2)
  ),

  'downgrade-eligible': rules.and(
    rules.lte('usage.percentage', 30),
    rules.eq('subscription.tier', 'premium'),
    rules.gte('subscription.consecutiveMonthsLow', 3)
  )
};

statefulEngine.on('triggered', (event) => {
  const actions = {
    'usage-threshold-80': () => {
      console.log('📧 80% usage warning email sent');
      // Email user about approaching limit
    },
    'usage-exceeded': () => {
      console.log('🚨 Usage limit exceeded - upgrade prompt shown');
      // Show upgrade modal
    },
    'upgrade-recommended': () => {
      console.log('⬆️ Upgrade recommendation sent');
      // Offer premium plan discount
    },
    'downgrade-eligible': () => {
      console.log('💡 Downgrade suggestion sent');
      // Suggest cost savings
    }
  };

  actions[event.ruleId]?.();
});

const accountData = {
  usage: {
    percentage: 85,
    current: 8500,
    limit: 10000
  },
  subscription: {
    tier: 'basic',
    consecutiveMonthsHigh: 3,
    consecutiveMonthsLow: 0
  }
};

statefulEngine.evaluateBatch(billingRules, accountData);
// 📧 80% usage warning email sent
// ⬆️ Upgrade recommendation sent

Logistics & Delivery

Delivery Tracking

const deliveryRules = {
  'delivery-delayed': rules.and(
    rules.gt('delivery.currentTime', 'delivery.estimatedTime'),
    rules.eq('delivery.status', 'in-transit')
  ),

  'location-updated': rules.and(
    rules.changed('delivery.currentLocation'),
    rules.eq('delivery.status', 'in-transit')
  ),

  'out-for-delivery': rules.and(
    rules.changedTo('delivery.status', 'out-for-delivery'),
    rules.isNotNull('delivery.driver')
  ),

  'delivered': rules.and(
    rules.changedTo('delivery.status', 'delivered'),
    rules.isNotNull('delivery.signedBy')
  ),

  'failed-delivery': rules.and(
    rules.changedTo('delivery.status', 'failed'),
    rules.gte('delivery.attemptCount', 3)
  )
};

statefulEngine.on('triggered', (event) => {
  const actions = {
    'delivery-delayed': () => {
      console.log('⏰ Delivery delayed notification sent');
      // SMS/Email to customer
    },
    'location-updated': () => {
      console.log('📍 Location updated');
      // Update tracking map
    },
    'out-for-delivery': () => {
      console.log('🚚 Out for delivery notification');
      // SMS with driver info
    },
    'delivered': () => {
      console.log('✅ Delivery confirmation sent');
      // Email receipt
    },
    'failed-delivery': () => {
      console.log('❌ Failed delivery - return to sender');
      // Initiate return process
    }
  };

  actions[event.ruleId]?.();
});

const deliveryData = {
  delivery: {
    status: 'out-for-delivery',
    currentLocation: 'Distribution Center',
    currentTime: '14:30',
    estimatedTime: '15:00',
    driver: { name: 'John', id: 'D123' },
    attemptCount: 1,
    signedBy: null
  }
};

statefulEngine.evaluateBatch(deliveryRules, deliveryData);
// 🚚 Out for delivery notification

Best Practices

1. Use Stateful Rules for Time-Series Data

Track changes in sensor data, user behavior, transactions

2. Combine Multiple Rules

Use batch evaluation for complex scenarios

3. Add Business Context

Include relevant business logic, not just technical checks

4. Monitor and Alert

Use event system for real-time notifications

5. Test with Real Data

Use production-like scenarios in testing

6. Performance Matters

Cache rules, order conditions efficiently

Stateful Rules

State change detection

Complex Validation

Multi-step validation

Performance Guide

Optimization tips

Deployment Guide

Production deployment

Examples

​E-commerce

Dynamic Pricing

Inventory Management

Fraud Detection

Promotions

​Dynamic Pricing

​Fraud Detection

​Healthcare

​Patient Monitoring

​Financial Services

​Transaction Monitoring

​IoT & Smart Home

​Smart Thermostat

​Content Moderation

​Social Media Platform

​SaaS Platform

​Usage-Based Billing

​Logistics & Delivery

​Delivery Tracking

​Best Practices

​Related

Stateful Rules

Complex Validation

Performance Guide

Deployment Guide

E-commerce

Dynamic Pricing

Fraud Detection

Healthcare

Patient Monitoring

Financial Services

Transaction Monitoring

IoT & Smart Home

Smart Thermostat

Content Moderation

Social Media Platform

SaaS Platform

Usage-Based Billing

Logistics & Delivery

Delivery Tracking

Best Practices

Related