document allowUndefinedFacts

Author: Cache Hamm

docs/engine.md

@@ -4,7 +4,7 @@ The Engine stores and executes rules, emits events, and maintains state.
 
 ## Methods
 
-### constructor([Array rules])
+### constructor([Array rules], Object [options])
 
 ```js
 let Engine = require('json-rules-engine').Engine
@@ -13,8 +13,20 @@ let engine = new Engine()
 
 // initialize with rules
 let engine = new Engine([Array rules])
+
+// initialize with options
+let options = {
+  allowUndefinedFacts: false
+};
+let engine = new Engine([Array rules], options)
 ```
 
+#### Options
+
+`allowUndefinedFacts` - By default, when a running engine encounters an undefined fact,
+an exception is thrown.  Turning this option on will cause the engine to treat
+undefined facts as falsey conditions.  (default: false)
+
 ### engine.addFact(String id, Function [definitionFunc], Object [options])
 
 ```js

docs/walkthrough.md

@@ -61,7 +61,9 @@ More on rules can be found [here](./docs/rules.md)
 
 ### Step 3: Define Facts
 
-Facts are constant values or pure functions.  Using the current example, if the engine were to be run, it would throw an error: "Undefined fact: 'age'".  So let's define some facts!
+Facts are constant values or pure functions.  Using the current example, if the engine were to be run, it would throw an exception: `Undefined fact:'age'` (note: this behavior can be disable via [engine options](./engine.md#Options)).
+
+Let's define some facts:
 
 ```js
 

src/engine.js

@@ -167,7 +167,7 @@ class Engine extends EventEmitter {
     debug(`engine::run runtimeFacts:`, runtimeFacts)
     runtimeFacts['success-events'] = new Fact('success-events', SuccessEventFact(), { cache: false })
     this.status = RUNNING
-    let almanac = new Almanac(this.facts, runtimeFacts, this.options)
+    let almanac = new Almanac(this.facts, runtimeFacts)
     let orderedSets = this.prioritizeRules()
     let cursor = Promise.resolve()
     // for each rule set, evaluate in parallel,