transaction-observer.js

observer || observer.cleanUp()

observer = (() => {
  // start config

  const THRESHOLD = 3000000

  // end config


  const getBigTransaction = (threshold) =>
    Array.from(document.querySelectorAll('market-ticker-page-row'))
      .map(mt => {
        const lis = mt.querySelectorAll('li')
        return [
          lis[0].innerText,
          parseFloat(lis[2].innerText.replace(',', '')) * parseFloat(lis[3].innerText),
          new Date().toLocaleDateString(),
          new Date().toLocaleTimeString(),
        ]
      })
      .filter(([name, transactionValue]) => name != '' && transactionValue != NaN)
      .filter(([_, transactionValue]) => transactionValue >= threshold)

  const getStore = () => {
    let store

     try {
       store = JSON.parse(localStorage.getItem('bigTransactions')) || []
     } catch {
       console.error('Stored transactions are malformed')
       store = []
     }
     
     return store
  }

  const updateStore = (bigTransactions) => {
    const store = getStore()
    const updatedStore = store
      .concat(bigTransactions)
      .filter((value, index, self) => {
        const storeIndexedByDateAndValue = self.map(([n, txn, date]) => [n, txn, date].toString())
        const itemWithOnlyDateAndValue = [value[0], value[1], value[2]].toString()
        return storeIndexedByDateAndValue.indexOf(itemWithOnlyDateAndValue) === index
      })
    localStorage.setItem('bigTransactions', JSON.stringify(updatedStore))
    localStorage.setItem('bigTransactionUpdatedAt', new Date().toLocaleString())
  } 

 

  const interval = setInterval(() => {
    const bigTransactions = getBigTransaction(THRESHOLD)
    updateStore(bigTransactions)
  }, 1000 * 10)

  const cleanUp = () => clearInterval(interval)

  const display = () => {
     const store = getStore()
     console.table(
       store
         .map(([name, transactionValue, date, time]) => ({ name, transactionValue, date, time })))
  }

  const download = () => {
    const csvContent = 'data:text/csv;charset=utf-8,' + getStore().map((row) => row.join(',')).join('\r\n')
    const encodedUri = encodeURI(csvContent)
    const link = document.createElement('a')
    link.setAttribute('href', encodedUri)
    link.setAttribute('download', `big_transactions ${new Date().toLocaleString()}.csv`)
    link.click()
    link.remove()
  }

  return { display, download, cleanUp }
})()