Google Tag Manager (GTM) server-side y BigQuery API: generar una base de datos de tu ‘ecommerce’ sin pasar por Google Analytics

//API's needed for this tag template to operate
const BigQuery = require('BigQuery');
const getAllEventData = require('getAllEventData');
const getRequestHeader = require('getRequestHeader');
const getTimestampMillis = require('getTimestampMillis');
const Math = require('Math');
const makeNumber = require('makeNumber');
const currentMoment = Math.round(getTimestampMillis()/1000);

//Tag code
const eventObject = getAllEventData();

//Code needed to generate a dynamic items array that is going to be sent to BigQuery
let itemsBigQueryArray = [];

for (let i = 0; i < eventObject.items.length; i++){
  
  itemsBigQueryArray[i] = {
    item_name: eventObject.items[i].item_name,
    item_id: eventObject.items[i].item_id,
    price: eventObject.items[i].price,
    item_brand: eventObject.items[i].item_brand,
    category: eventObject.items[i].item_category,
    variant: eventObject.items[i].item_variant,
    quantity: eventObject.items[i].quantity
   };
}

const bigQueryObject = {
  date: currentMoment,
  transaction_id: eventObject.transaction_id,
  affiliation: eventObject.affiliation,
  //Value, tax and shipping are string values, converting them to number value with makeNumber() API to send to BigQuery table as a number to operate with later
  value: makeNumber(eventObject.value),
  tax: makeNumber(eventObject.tax),
  shipping: makeNumber(eventObject.shipping),
  currency: eventObject.currency,
  item: itemsBigQueryArray,
  //'Country' and 'city' are generated from the incoming request headers
  country: getRequestHeader('X-Appengine-Country'),
  city: getRequestHeader('X-Appengine-City')
};
//Object containing the BigQuery project, data set and table id's to which data is going to be written
const bigQueryInfo = {
  projectId: data.projectName,
  datasetId: data.datasetName,
  tableId: data.tableName,
};
//Faulty Values Object
const faultyValuesObject = {
  ignoreUnknownValues: false,
  skipInvalidRows: false,
};
//BigQuery API insert operation
BigQuery.insert(bigQueryInfo, [bigQueryObject], faultyValuesObject, data.gtmOnSuccess(), data.gtmOnFailure());