Cross-Currency Payment | XRPL Development in JavaScript - Level 3

This guide explains cross-currency payments by dealing with A.USD issued by Issuer A and B.EUR issued by Issuer B.

In the previous section, we confirmed that Alice can place an offer to sell A.USD issued by Issuer A and buy B.EUR issued by Issuer B, allowing Daniel to send A.USD to Charlie (liquidity is available).

In this section, let’s actually send A.USD from Daniel to Charlie!

Prerequisites

Alice has already placed an offer to sell A.USD issued by Issuer A and buy B.EUR issued by Issuer B, thereby providing liquidity.

Daniel needs to make a payment to Charlie, who wants to receive A.USD. However, Daniel currently does not hold any A.USD; he only has XRP and B.EUR issued by Issuer B. Daniel is considering to exchange his B.EUR for A.USD.

After searching for someone willing to exchange B.EUR for the desired amount of A.USD, Daniel confirms that such a person exists. Now, he will proceed to send A.USD to Charlie by exchanging his B.EUR.

Creating the Script

Create a new file named crossCurrencyPayment.js in your project directory.

Paste the following code into crossCurrencyPayment.js.

import xrpl from 'xrpl';
import { wallets } from './wallets.js';
import { sendPayment } from './utils/payment.js';

const client = new xrpl.Client('wss://s.altnet.rippletest.net:51233');

const main = async () => {
    await client.connect();

    const { issuerA, issuerB, alice, bob, charlie, daniel } = wallets;

    await sendPayment(
        client,
        daniel,
        { currency: 'USD', issuer: issuerA.address, value: '100' }, // Currency Charlie wants to receive: A.USD
        charlie.address,
        {
            sendMax: { currency: 'EUR', issuer: issuerB.address, value: '100' } // Currency Daniel wants to pay: B.EUR
        }
    );

    await client.disconnect();
};

main().catch(console.error);

Running the Script

Execute the following command in the command line to run the script.
Terminal window
```
node crossCurrencyPayment.js
```

If you see logs like the following, the operation was successful.

Payment sent from rf6R7pFgytT9JKjMVjKqeTv6MeDTrbNw3 to rnP7Q6LaejYi7oaN4qJHkKhnESZYAyVQwh: {
    id: 12,
    result: {
        Account: 'rf6R7pFgytT9JKjMVjKqeTv6MeDTrbNw3', // Daniel's address
        Amount: {
            currency: 'USD', // A.USD
            issuer: 'rfkJ7Uz6NrNV1FdbmKB5wepoim51KFpYQp', // Issuer A's address
            value: '100' // 100 A.USD
        },
        DeliverMax: {
            currency: 'USD',
            issuer: 'rfkJ7Uz6NrNV1FdbmKB5wepoim51KFpYQp',
            value: '100'
        },
        Destination: 'rnP7Q6LaejYi7oaN4qJHkKhnESZYAyVQwh', // Charlie's address
        Fee: '12',
        Flags: 0,
        LastLedgerSequence: 1053776,
        SendMax: { // Daniel's maximum payment limit
            currency: 'EUR', // B.EUR
            issuer: 'rstM9rxhKo4N4WEaQgQmQSPQRgZqkhHkaU', // Issuer B's address
            value: '100' // 100 B.EUR
        },
        Sequence: 1046430,
        SigningPubKey: 'EDEC83B1B5D761F21A9625E88C70EE68CE5D5496B513DC6295CEDA7905065DD51A',
        TransactionType: 'Payment',
        TxnSignature: '9E691B08DC3CCE1AA91B0141AD428D04359E13A2E248CE6B3E449BF2254B302563902D224289435CF0DCDCB643169DD761D34631D44B3008C6C595DA2E7D8201',
        ctid: 'C010143E00000001',
        date: 770232142,
        hash: '4B5BAE83A8D0841DC867C115B625265DDF2ACEC1954E5F8AEC097DA489761AA3',
        inLedger: 1053758,
        ledger_index: 1053758,
        meta: {
            AffectedNodes: [Array],
            TransactionIndex: 0,
            TransactionResult: 'tesSUCCESS', // 成功
            delivered_amount: [Object]
        },
        validated: true
    },
    type: 'response'
}

At this point, verify the following using the Explorer:

Alice’s balance of A.USD has decreased to 900, and her balance of B.EUR has increased to 1,100.
Charlie’s balance of A.USD has increased to 1,100.
Daniel’s balance of B.EUR has decreased to 900.

This demonstrates that the XRPL has a unique feature that allows for “simultaneous payment and swap (exchange)“.

Summary

Cross-currency payments are a unique feature of the XRPL, which has a native DEX, and it is one of its most representative functions.

In the XRPL, even if the currencies (tokens) are issued by different issuers, as long as there is liquidity, you can deliver the currency you want to pay in as the currency the recipient wants to receive.

In the next section, we will delve deeper into the topic of cross-currency payments.