static/node_modules/mongoose/lib/helpers/each.js

'use strict';

module.exports = function each(arr, cb, done) {
  if (arr.length === 0) {
    return done();
  }

  let remaining = arr.length;
  let err = null;
  for (const v of arr) {
    cb(v, function(_err) {
      if (err != null) {
        return;
      }
      if (_err != null) {
        err = _err;
        return done(err);
      }

      if (--remaining <= 0) {
        return done();
      }
    });
  }
};