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+'use strict'
+
+/*
+ * This is a basic example demonstrating a condition that compares two facts
+ *
+ * Usage:
+ *   node ./examples/08-fact-comparison.js
+ *
+ * For detailed output:
+ *   DEBUG=json-rules-engine node ./examples/08-fact-comparison.js
+ */
+
+require('colors')
+let Engine = require('../dist').Engine
+
+/**
+ * Setup a new engine
+ */
+let engine = new Engine()
+
+/**
+ * Rule for determining if account has enough money to purchase a $50 gift card product
+ *
+ * customerAccount (in euros) >= $50 gift card
+ */
+let rule = {
+  conditions: {
+    all: [{
+      // extract 'balance' from the 'customer' account type
+      fact: 'account',
+      path: '.balance',
+      params: {
+        accountType: 'customer'
+      },
+
+      operator: 'greaterThanInclusive',  // >=
+
+      // "value" in this instance is an object containing a fact definition
+      // fact helpers "path" and "params" are supported here as well
+      value: {
+        fact: 'product',
+        path: '.price',
+        params: {
+          productId: 'giftCard'
+        }
+      }
+    }]
+  },
+  event: { type: 'customer-can-afford-gift-card' }
+}
+engine.addRule(rule)
+
+engine.addFact('account', (params, almanac) => {
+  // get account list
+  return almanac.factValue('accounts')
+    .then(accounts => {
+      // use "params" to filter down to the type specified, in this case the "customer" account
+      let customerAccount = accounts.filter(account => account.type === params.accountType)
+      // return the customerAccount object, which "path" will use to pull the "balance" property
+      return customerAccount[0]
+    })
+})
+
+engine.addFact('product', (params, almanac) => {
+  // get product list
+  return almanac.factValue('products')
+    .then(products => {
+      // use "params" to filter down to the product specified, in this case the "giftCard" product
+      let product = products.filter(product => product.productId === params.productId)
+      // return the product object, which "path" will use to pull the "price" property
+      return product[0]
+    })
+})
+
+/**
+ * Register listeners with the engine for rule success and failure
+ */
+let facts
+engine
+  .on('success', (event, almanac) => {
+    console.log(facts.userId + ' DID '.green + 'meet conditions for the ' + event.type.underline + ' rule.')
+  })
+  .on('failure', rule => {
+    console.log(facts.userId + ' did ' + 'NOT'.red + ' meet conditions for the ' + rule.event.type.underline + ' rule.')
+  })
+
+// define fact(s) known at runtime
+let productList = {
+  products: [
+    {
+      productId: 'giftCard',
+      price: 50
+    }, {
+      productId: 'widget',
+      price: 45
+    }, {
+      productId: 'widget-plus',
+      price: 800
+    }
+  ]
+}
+
+let userFacts = {
+  userId: 'washington',
+  accounts: [{
+    type: 'customer',
+    balance: 500
+  }, {
+    type: 'partner',
+    balance: 0
+  }]
+}
+
+// compile facts to be fed to the engine
+facts = Object.assign({}, userFacts, productList)
+
+engine
+  .run(facts)  // first run, user can afford a gift card
+  .then(() => {
+    // second run; a user that cannot afford a gift card
+    userFacts = {
+      userId: 'jefferson',
+      accounts: [{
+        type: 'customer',
+        balance: 30
+      }]
+    }
+    facts = Object.assign({}, userFacts, productList)
+    return engine.run(facts)
+  })
+  .catch(console.log)
+
+/*
+ * OUTPUT:
+ *
+ * washington DID meet conditions for the customer-can-afford-gift-card rule.
+ * jefferson did NOT meet conditions for the customer-can-afford-gift-card rule.
+ */