What can CosmJS do for me?

Calculating transaction IDs

If you have a list of complete transactions like this

{
  "txs": [
    "9AEoKBapCjCMTXENChQmiMbn/hEgc2noEV+vJkHASIhPShIUU7SyT3IQK/OJv+xZUz5LP9dR4FQKPpIdLk4KFCaIxuf+ESBzaegRX68mQcBIiE9KEhRTtLJPchAr84m/7FlTPks/11HgVBoMCgV1YXRvbRIDMTQ1EhAKCgoFdWF0b20SATAQ4KcSGmoKJuta6YchA9E/2C2Tibu+oguuOS2AwO9sGwy1ejes+u8hBdGJ2guiEkBZ7JjaZhENW56nbqaUH0SdgnuWHmPlPfgWs2LVwbOj6BDacUL+vcKqd4vxmkYRB9ORmqnDlj9ppaupmIPnOQuK",
    "ywEoKBapCkWoo2GaChQxrczb/flZmTC8mDh3uKwKyZCnpRIUWYCZ0lvC4PM8HrDaaR1oSU65PLoaEwoFdWF0b20SCjM4MDQwMDAwMDASEgoMCgV1YXRvbRIDNzUwEMCaDBpqCibrWumHIQMgfOISgYzdsLJnQtnhdT6c+pd1cZX0iiaWLE2i+Fa6xBJAIvmDdjJstWPWqshZxCtMXWXL1CBw06a9oYH8f2l7f19I5RsDDYJz1QTnKwor765rLsdAcF+5ucCBnkUnvy7I+g==",
    "twEoKBapCjCMTXENChQkQV2iWcShdar5UshUoWev/JUSfxIUyTRRx8hJmGRpUL1G+yw8xXQRSHsSEwoNCgV1YXRvbRIEMjUwMBDAzyQaagom61rphyEC1bbqM5eBuRSZ/jeQH1o25g7ybaQw3BlY4zQWmJb+k2QSQOSikSCd7AkDDjeCoNwdhdwgEOPiIZIHzF8TCSQSVdA/Iru/g9xE5eZTA4Cg2Q48idWyIHadYME5cKhVm3S8lHw=",
    "4gIoKBapCkOSHS5OChQ9NPQdHwRlRIc1MUP7Vy+gGRKtixIUYmtWnpmEfXd8qa3Khj8v1Xb//7oaEQoFdWF0b20SCDEwMDAwMDAwCkOSHS5OChQ9NPQdHwRlRIc1MUP7Vy+gGRKtixIUppAElPH3PNriuvHIuI/1/AuKM5waEQoFdWF0b20SCDEwMDAwMDAwCkOSHS5OChQ9NPQdHwRlRIc1MUP7Vy+gGRKtixIUyTRRx8hJmGRpUL1G+yw8xXQRSHsaEQoFdWF0b20SCDEwMDAwMDAwEhQKDgoFdWF0b20SBTIxODc5EJS1NRpqCibrWumHIQIT+U7tHv1kX5BoKGClAbKOf4nTI32tfFVX+AnedBYFnhJA/AedifYkknYTGcztoNn3VH7gMpeJXGsUxydWUMJ6wC8IT8uV5UWeHdmW0HbVsjRSxyKPDO+NLJbO35zwb1cT5CILTGVkZ2VyIExpdmU="
  ]
}

(from Cosmos Hub height 2421996), you can calculate a transaction ID like this:

import { Sha256 } from "@cosmjs/crypto";
import { fromBase64, toHex } from "@cosmjs/encoding";

const tx = "9AEoKBapCjCMTXENChQmiMbn/hEgc2noEV+vJkHASIhPShIUU7SyT3IQK/OJv+xZUz5LP9dR4FQKPpIdLk4KFCaIxuf+ESBzaegRX68mQcBIiE9KEhRTtLJPchAr84m/7FlTPks/11HgVBoMCgV1YXRvbRIDMTQ1EhAKCgoFdWF0b20SATAQ4KcSGmoKJuta6YchA9E/2C2Tibu+oguuOS2AwO9sGwy1ejes+u8hBdGJ2guiEkBZ7JjaZhENW56nbqaUH0SdgnuWHmPlPfgWs2LVwbOj6BDacUL+vcKqd4vxmkYRB9ORmqnDlj9ppaupmIPnOQuK";
const transactionHash = new Sha256(fromBase64(tx)).digest();
const transactionId = toHex(transactionHash).toUpperCase();