index.js
function iteratorFactory(callback) {
  return iterator

  function iterator(parent) {
    var children = parent && parent.children

    if (!children) {
      throw new Error('Missing children in `parent` for `modifier`')
    }

    return iterate(children, callback, parent)
  }
}
function iteratorFactory(callback) {
  return iterator

  function iterator(parent) {
    var children = parent && parent.children

    if (!children) {
      throw new Error('Missing children in `parent` for `modifier`')
    }

    return iterate(children, callback, parent)
  }
}
function iteratorFactory ( callback ) { return iterator function iterator ( parent ) { var children = parent && parent . children if ( ! children ) { throw new Error ( 'Missing children in `parent` for `modifier`' ) } return iterate ( children , callback , parent ) } }
Turn `callback` into a `iterator' accepting a parent.
Turn callback into a iterator accepting a parent .