JavaScript is Dead. Long Live JavaScript(peter.michaux.ca)

    for (var i=0, ilen=elements.length; i<ilen; i++) {
        var element = elements[i];
        let (num = i) {
            LIB_addEventListener(element, function(event) {
                alert('I was originally number ' + num);
            });
        };
    }

    for (let i=0, ilen=elements.length; i<ilen; i++) {
        let element = elements[i];
        LIB_addEventListener(element, function(event) {
            alert('I was originally number ' + i);
        });
    }

    elements.forEach(function (element, i) {
        LIB_addEventListener(element, function(event) {
            alert('I was originally number ' + i);
        });
    });

  function(a = 1, b = "Smith", option = {}) { .. }

  func({ a: 1, b: "Smith", option: { .. });

  var opt = config.option || {};

  Q.each(arr, function(i) {
     this.rocks();
     arr.pop(); // watch out doing this in the loop
     arr.push('foo'); // watch out doing this in the loop
  });

  Q.each(obj, function(k) {
     this.rocks();
     delete obj[k]; // should be safe maybe
  });

  var p = Q.pipe(crazy stuff involving pipes and callbacks)
  doSql("SELECT * FROM users", p.fill('users'));

  getUsers = Q.getter(getUsers); // turns it into a really  smart getter

  getUsers = Q.batch(getUsers); // turns into into a batched getter