param-enforcer.js

// idea 1 - use JOI (or similar) at the router level
let params = {
  query: {
    limit: Joi.number().integer().min(1).max(100).default(10)
  }
}
server.get("/horse", enforceParams(params), controller.myRoute)

// idea 2 - use JOI (or similar) at the controller level
async function myRoute(req, res) {
  let params =  {
    query: {
      accountId: Joi.string(),
      limit: Joi.number().integer().min(1).max(100).default(10)
    }
  }
  enforceParams(req, params)
  /* ... other stuff ... */
}

// idea 3 - manually using a custom Error object
async function myRoute(req, res) {
  if (!req.params.accountId) {
    throw new MissingParamError("Missing required accountId")
  }
  if (typeof req.query.limit !== 'number') {
    throw new MissingParamError("Expected limit to be a number")
  }
  /* ... other stuff ... */
}

// idea 4 - decorators
@params({
  query: {
    accountId: Joi.string(),
    limit: Joi.number().integer().min(1).max(100).default(10)
  }
})
function myRoute(req, res) {}

// idea 5 - use flow, but then transpile with a plugin to convert to somethign like 3?
async function myRoute(req, res) {
  let params: { limit?: number, accountId: string } = req.params
}
// converts with a babel plugin to
async function myRoute(req, res) {
  let params = req.params
  if (typeof params.accountId !== 'string') {
    throw new MissingParamError("accountId must be a string")
  }
}