a1.js

var b = require('sandboxed-module').require('./b', {});
b.foo();

a2.js

var item = [];
require('./c')(item);

b.js

exports.foo = function() {
  var item = [];
  var c = require('./c');
  console.log('BEFORE Constructor check: ' + (item.constructor === Array));
  console.log('BEFORE Instanceof check: ' + (item instanceof Array));
  console.log('BEFORE Array.isArray check: ' + Array.isArray(item));
  c(item);
}

c.js

module.exports = function (item) {
  console.log('AFTER Constructor check: ' + (item.constructor === Array));
  console.log('AFTER Instanceof check: ' + (item instanceof Array));
  console.log('AFTER Array.isArray check: ' + Array.isArray(item));
}

package.json

{
  "name": "foo",
  "version": "0.0.0",
  "dependencies": {
    "sandboxed-module": "0.1.3"
  }
}