generatorIteratorExample.js

// Ref: 
//	1. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Iterators_and_Generators 
//  2. https://davidwalsh.name/es6-generators

// ------------------------------------

function makeIterator(array) {
    var nextIndex = 0;
    
    return {
       next: function() {
           return nextIndex < array.length ?
               {value: array[nextIndex++], done: false} :
               {done: true};
       }
    };
}

var it = makeIterator(['yo', 'ya']);
console.log(it.next()); // 'yo'
console.log(it.next()); // 'ya'
console.log(it.next());  // true

// ------------------------------------

function* idMaker() {
  var index = 0;
  while(true){
    	yield index++;
  	}  	
}

var gen = idMaker();

console.log(gen.next()); // 0
console.log(gen.next()); // 1
console.log(gen.next()); // 2

// ------------------------------------
var myIterable = {};
myIterable[Symbol.iterator] = function* () {
    yield 1;
    yield 2;
    yield 3;
};

for (let value of myIterable) { 
    console.log(value); 
}

// ------------------------------------

function *foo() {
    var x = 1 + (yield "foo");
    console.log('x', x);
}

var it = foo();

console.log(it.next());
console.log(it.next(100));

// ------------------------------------
// note: `foo(..)` here is NOT a generator!!
function foo(x) {
    console.log("x: " + x);
}

function *bar() {
    yield; // just pause
    foo( yield ); // pause waiting for a parameter to pass into `foo(..)`
}

var it = bar();

console.log(it.next());
console.log(it.next(100));

// ------------------------------------

function *foo() {
    yield 1;
    yield 2;
    yield 3;
    yield 4;
    yield 5;
}

var it = foo();
console.log('it', it.next());
console.log('it', it.next());
console.log('it', it.next());
console.log('it', it.next());
console.log('it', it.next());
console.log('it', it.next());

// ------------------------------------

function *foo(x) {
    var y = 2 * (yield (x + 1));
    var z = yield (y / 3);
    return (x + y + z);
}

var it = foo( 5 );

// note: not sending anything into `next()` here
console.log( it.next() );       // { value:6, done:false }
console.log( it.next( 12 ) );   // { value:8, done:false }
console.log( it.next( 13 ) );   // { value:42, done:true }