Helper module for tv4 to validate against MongoDB ObjectId.
$ npm install --save tv4 tv4-mongodb
const assert = require("assert");
const tv4 = require("tv4");
const validator = tv4.freshApi();
validator.addFormat(require("tv4-mongodb"));
const schema = { type: "string", format: "bson-objectid" };
assert(validator.validate("585d4f15d890997a4fb0d2e8", schema)); // Valid ObjectId
assert(!validator.validate("585d4f15d890997a4fb0d2z8", schema)); // Invalid ObjectId