NodeJS script to run a Nimiq (full) node to listen to all transactions getting added to the mempool.

node-nimiq-mempool.js

const Nimiq = require('@nimiq/core');

Nimiq.load().then(async function() {
    // Configure for Testnet. For Mainnet, use main().
    Nimiq.GenesisConfig.test();

    // Instantiate a config builder.
    const configBuilder = Nimiq.Client.Configuration.builder();
    
    // Require a mempool
    configBuilder.feature(Nimiq.Client.Feature.MEMPOOL);
    
    /**
     * The above creates a so-called "light" client. However, light clients can currently not
     * establish consensus, because the accounts-tree is too big.
     * So you will need to run a full node to listen to _all_ transactions:
     */
    configBuilder.feature(Nimiq.Client.Feature.LOCAL_HISTORY);

    // Create a client based on your configuration,
    // it will automatically connect to the network.
    const client = configBuilder.instantiateClient();
    
    client.mempool.addTransactionAddedListener(async (hash) => {
        const tx = await client.getTransaction(hash);
        
        // Do something with `tx`
        // The object's type is this:
        // https://github.com/nimiq/core-js/blob/master/dist/types.d.ts#L281
        const sender = tx.sender.toUserFriendlyAddress();
        const recipient = tx.recipient.toUserFriendlyAddress();
        const valueInNim = Nimiq.Policy.lunasToCoins(tx.value);
    });
});