docs: function ArrayEmitter(arr, op) {
    op = op || {};
    this.readable = true;
    this.paused   = !!op.pause;
  
    this.arr = arr || [];
    this.len = (arr instanceof Array) 
      ? arr.length
      : Object.keys(arr).length;
    this.i   = 0;
    this.op  = op;
  
    if (!this.paused) nextTick(emit.bind(this));
  
  }