This package is now deprecated. HTTP status codes used by Mapistry now live in an enum in mapistry-shared. Replacement is straightforward, and should be done gradually as code using the httpStatusCodes package is touched:

// in existing code
httpCodes = require('httpStatusCodes');
....
ret = httpCodes.SUCCESS

// replace with
import { HttpStatusCode } from 'mapistry-shared';
...
ret = HttpStatusCode.SUCCESS