primitive asyncMap and asyncForeach methods for primitive environment

asyncForeach.js

function asyncForeach(array, fn, atEnd) {
  var at = -1;
  function next(shouldBreak) {
    if (shouldBreak || ++at == array.length) {
      if (atEnd) {
        setTimeout(atEnd);
      }
    } else {
      setTimeout(fn, 0, array[at], next);
    }
  }

  next();
}

asyncMap.js

function asyncMap(array, fn, atEnd) {
  var at = -1;
  var temp = new Array(array.length);
  function next(value, shouldBreak) {
    if (at != -1) temp[at] = value;
    if (shouldBreak || ++at == array.length) {
      if (atEnd) {
        setTimeout(atEnd, 0, temp);
      }
    } else {
      setTimeout(fn, 0, array[at], next);
    }
  }

  next();
}

examples.js

asyncForeach([1, 2, 3], function (item, done) {
  console.log('item: ', item);
  setTimeout(done, 1000);
}, function () {
  console.log('end');
})


asyncMap([1, 2, 3], function (item, done) {
  console.log('item: ', item);
  setTimeout(done, 1000, item * 2);
}, function (array) {
  console.log('end', array);
})

// break the loop
asyncForeach([1, 2, 3], function (item, done) {
  console.log('item: ', item);
  done(true);
}, function () {
  console.log('end');
});

asyncMap([1, 2, 3], function (item, done) {
  console.log('item: ', item);
  done(item * 2, true);
}, function (array) {
  console.log('end', array);
})

sync.js

function sync() {
  var i = 0;
  var arr = [];
  return {
    begin: function () {
      i++;
    },

    end: function () {
      return new Promise(function (resolve) {
        arr.push(resolve);
        i--;
        if (i == 0) {
          arr.forEach(function (x) { x(); });
        }
      });
    }
  }
}

//example

var s = sync();
for (var i = 0; i < 5; i++) {
  (async function (i) {
    s.begin();
    console.log(i, 'begin');
    await new Promise(x => setTimeout(x, i*750));
    console.log(i, 'ready');
    await s.end();
    console.log(i, 'play');
  })(i)
}

//0 "begin"
//1 "begin"
//2 "begin"
//3 "begin"
//4 "begin"

//0 "ready"
//1 "ready"
//2 "ready"
//3 "ready"
//4 "ready"

//0 "play"
//1 "play"
//2 "play"
//3 "play"
//4 "play"