Version value returned from customer list API

The output from the customers API in the online API explorer ( includes a “version” key with a 64-bit integer value. (Reference doc here: GET /v2/customers - Square API Reference) However, when I call the API from my NodeJS/Express code, an “n” is appended to the value. For example, the online API explorer returns " version: 1 " regardless of the method I choose (cURL, Python, NodeJS, etc) but when I call it from my Node server it returns " version: 1n." The “n” makes the JSON.stringify() method believe it’s trying to serialize a big int value and returns an error. Please advise if this is intentional, or an error on my part, and/or a course of action forward. Thanks!

Here is a snippet of the API output from my server and the associated error message:

version: 2n
TypeError: Do not know how to serialize a BigInt
    at JSON.stringify (<anonymous>)

Here is a snippet of my code for the Express route that calls the customers API:

app.get('/customers', async (req, res)=>{
  const customersApi = client.customersApi;

  try {
    const response = await customersApi.listCustomers();
  } catch(error) {

Hello Michael,

I believe the issue is JSON.stringify() doesn’t support BigInt (MDN docs).

The Node SDK treats the version field as a bigint (customer object reference). And adding suffix ‘n’ is a permitted way to represent bigint (MDN docs).

Please let us know if this was helpful.


Yes, the n suffix is indeed a permitted way to represent bigint values. OK, at least I know for sure that it wasn’t a bug. Can you explain why it doesn’t appear in the online API tool? Just curious.