callbag-pairwise/dist/callbag-pairwise.js

👜 Callbag operator that emits the previous and current values as an array.

'use strict';

function pairwise(source) {
  return function (start, sink) {
    if (start !== 0) return;
    var inited = 0;
    var prev;
    var current;
    var talkback;
    source(0, function (type, data) {
      if (type === 0) {
        talkback = data;
      }

      if (type !== 1) {
        sink(type, data);
        return;
      }
      var _ref = [current, data];
      prev = _ref[0];
      current = _ref[1];
      inited++;

      if (inited < 2) {
        talkback(1);
        return;
      }

      sink(1, [prev, current]);
    });
  };
}

module.exports = pairwise;