through2-concurrent.js
function callOnFinish (original) {
    return function (callback) {
      if (concurrent === 0) {
        original.call(this, callback);
      } else {
        pendingFinish = original.bind(this, callback);
      }
    }
  }
function callOnFinish (original) {
    return function (callback) {
      if (concurrent === 0) {
        original.call(this, callback);
      } else {
        pendingFinish = original.bind(this, callback);
      }
    }
  }
function callOnFinish ( original ) { return function ( callback ) { if ( concurrent === 0 ) { original . call ( this , callback ) ; } else { pendingFinish = original . bind ( this , callback ) ; } } }
Flush is always called only after Final has finished to ensure that data from Final gets processed, so we only need one pending callback at a time
Flush is always called only after Final has finished to ensure that data from Final gets processed so we only need one pending callback at a time