ES6 Generators

example1.js

setTimeout(function(){
  _get("/something.ajax?greeting", function(err, greeting) {
    if (err) { console.log(err); throw err; }
    _get("/else.ajax?who&greeting="+greeting, function(err, who) {
      if (err) { console.log(err); throw err; }
      console.log(greeting+" "+who);
    });
 });
}, 1000);

example10.js

genny.run(function* (resume) {
  _get("test1.txt", resume());
  _get("test2.txt", resume());
  var res1 = yield resume, res2 = yield resume; // step 1
  var res3 = yield _get("test3.txt", resume()); // step 2
  console.log(res1 + res2);
});

example2.js

sync(function* (resume) {
  try (e) {
    yield setTimeout(resume, 1000);
    var greeting = yield _get('/something.ajax?greeting', resume)
    var who = yield _get('/else.ajax?who&greeting=' + greeting, resume)
    console.log(greeting + ' ' + who)
  }
  catch (e) {
    console.log(e);
    throw e;  
  } 
});

example3.js

function* fibonacci() {
  var a = 0, b = 1, c = 0;

  while (true) {
    yield a;
    c = a;
    a = b;
    b = c + b;
  }
}

function run() {
  var seq = fibonacci();
  console.log(seq.next().value); // 0
  console.log(seq.next().value); // 1
  console.log(seq.next().value); // 1
  console.log(seq.next().value); // 2
  console.log(seq.next().value); // 3
  console.log(seq.next().value); // 5
}

run();

example4.js

function* powGenerator() {
  var result = Math.pow(yield "a", yield "b");
  return result;
}

var g = powGenerator();
console.log(g.next().value);   // "a", from the first yield
console.log(g.next(10).value); // "b", from the second
console.log(g.next(2).value);  // 100, the result

example5.js

function* powGenerator() {
  var result = Math.pow(----10----, yield "b");
  return result;
}

example6.js

function* powGenerator() {
  var result = Math.pow(----10----, ----2----);
  return result;
}

example7.js

// **************
// framework code

function sync(gen) {
  var iterable, resume;

  resume = function(err, retVal) {
    if (err) iterable.raise(err);
    iterable.next(retVal); // raise!  
  };

  iterable = gen(resume);
  iterable.next();
}

function _get(url, callback) {
  var x = new XMLHttpRequest();

  x.onreadystatechange = function() {
    if (x.readyState == 4) {
      callback(null, x.responseText);
    }
  };

  x.open("GET", url);
  x.send();
}

// ****************
// application code

sync(function* (resume) {
  log('foo');
  var resp = yield _get("http://localhost:8080/blix.txt", resume); // suspend!
  log(resp);
});

log('bar'); // not part of our generator function’s body

example8.js

try {
  firstAsync(function(err, a) {
    if (err) { console.log(err); throw err; }
    secondAsync(function(err, b) {
      if (err) { console.log(err); throw err; }
      thirdAsync(function(err, c) {
        if (err) { console.log(err); throw err; }
        callback(a, b, c);
      });    
    });
  }); 
}
catch (e) {
  console.log(e);
}

example9.js

function sync(gen) {
  var iterable, resume;

  resume = function(err, retVal) {
    if (err) iterable.raise(err); // raise!
    iterable.next(retVal);
  };

  iterable = gen(resume);
  iterable.next();
}

sync(function* (resume) {
  try {
    var x = firstAsync(resume);
    var y = secondAsync(resume);
    var z = thirdAsync(resume);
    // … do something with your data
  }
  catch (e) {
    console.log(e); // will catch errors from any of the three calls
  }
});