dump()

The dump method outputs the results at that moment and then continues processing:

collect([1, 2, 3, 4])
  .dump()
  .map(item => item * 2)
  .dump();

//=> Collection { items: [ 1, 2, 3, 4 ] }
//=> Collection { items: [ 2, 4, 6, 8 ] }

View source on GitHub