Upsert by external ID

export async function upsertByExternalId({ host, token, recordType, externalId, body, replace }) {
  const qs = replace ? `?replace=${encodeURIComponent(replace)}` : ''
  const url = `https://${host}.suitetalk.api.netsuite.com/services/rest/record/v1/${recordType}/eid:${encodeURIComponent(externalId)}${qs}`

  const res = await fetch(url, {
    method: 'PUT',
    headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  })
  if (res.status !== 204) throw new Error(`Upsert ${res.status}: ${await res.text()}`)

  // NetSuite answers 204 with the record URL in Location
  return res.headers.get('location')?.split('/').pop()
}

const id = await upsertByExternalId({
  host: '1234567-sb1',
  token,
  recordType: 'salesOrder',
  externalId: `SHOPIFY-${order.id}`,
  replace: 'item', // replace item lines on update instead of appending
  body: {
    entity: { id: customerId },
    otherRefNum: order.name,
    item: { items: order.lines.map((l) => ({ item: { id: l.nsItemId }, quantity: l.qty, rate: l.price })) },
  },
})