Infinite Fibonacci sequence using generators

Author: vasanthk

3-generators.js

@@ -11,6 +11,12 @@
 /**
 * What are generators?
 * Generators are functions which can be exited and later re-entered. Their context (variable bindings) will be saved across re-entrances.
+*
+* In computer science, a generator is a special routine that can be used to control the iteration behaviour of a loop. In fact, all generators are iterators.
+* A generator is very similar to a function that returns an array, in that a generator has parameters, can be called, and generates a sequence of values.
+* However, instead of building an array containing all the values and returning them all at once, a generator yields the values one at a time,
+* which requires less memory and allows the caller to get started processing the first few values immediately. In short, a generator looks like a function but behaves like an iterator.
+*
 */
 
 // Two things distinguish genFunc from a normal function declaration:
@@ -345,4 +351,26 @@ genObj1.throw(new Error('Problem!'));
 function* genFunc() {
 }
 genFunc().throw(new Error('Problem!'));
-// Error: Problem!
+// Error: Problem!
+
+
+/**
+* Extras:
+* Infinite Fibonacci sequence using generators
+*/
+
+function* fibonacci() {
+let [prev, curr] = [0, 1];
+while (true) {
+yield curr;
+[prev, curr] = [curr, prev + curr];
+}
+}
+
+var gen = fibonacci();
+console.log(gen.next().value); // 1
+console.log(gen.next().value); // 1
+console.log(gen.next().value); // 2
+console.log(gen.next().value); // 3
+console.log(gen.next().value); // 5
+console.log(gen.next().value); // 8