TypeScript Type Definitions for the XUMM API

Typescript type Definitions are available in the XUMM SDK package:
https://www.npmjs.com/package/xumm-sdk

Source:
https://github.com/XRPL-Labs/XUMM-SDK

import {Types} from 'xumm-sdk'

// Sample using XUMM SDK types
const PaymentPayload: Types.CreatePayload = {
  txjson: {
    TransactionType : 'Payment',
    Destination : 'rPEPPER7kfTD9w2To4CQk6UCfuHM9c6GDY',
    DestinationTag: 495,
    Amount: '1337'
  }
}

👍

There's an SDK for Javascript & Typescript

Please note that, instead of calling the XUMM API yourself, you can use the XUMM SDK instead. Here's a tutorial.