rafa/src/core/ArrayEnumerator.js

Rafa.js is a Javascript framework for building concurrent applications.

// # constructor(Array): ArrayEnumerator
// An Enumerator that calls a callback for each item in the provided Array.
function ArrayEnumerator(array) {
  let len = array && array.length;
  if (!len) return new EmptyEnumerator();
  this.array = array;
  this.idx = 0;
  this.len = len;
}

inherit(ArrayEnumerator, Enumerator, {

  // # next(callback: Message => _)
  // Execute a callback function, passing the next value wrapped in a Message.
  // If the value is the last item in the array, then return the value
  // wrapped in a DoneMessage.
  next(callback) {
    let { idx, len } = this;
    let M = this.Message;

    if (idx === len) throw this.CompleteError;

    let item = this.array[idx++];
    if (idx === len) M = this.DoneMessage;
    this.idx = idx;

    if (item instanceof Error)
      M = this.ErrorMessage;

    callback(new M(item));
  }
});