Example code on Ubuntu+node.js gives error re “await”

Question

Updated: added full code below.

I'm trying to run the "Creating a payment transaction" example but the error I get is

const account = await server.loadAccount(sourcePublicKey);
                ^^^^^    
SyntaxError: await is only valid in async function

I am running this on Ubuntu 18.04 (Digital Ocean) w/ Node.js v8.10 as instructed and have edited the code so that it uses the test network and key pairs I have set up w/ the laboratory.

So what do I need to do to my setup to get this example to work, or is there a workaround using promise? I just want to do a test transfer of some lumens on the test network.

Here's the full code - it's the same as what is provided as example code on the stellar developer site at link above. (The secret key is for a testnet address so I don't mind sharing it).

const StellarSdk = require('stellar-sdk');

const sourceSecretKey = 'SC5XS6G54A2ILNQRZF4H2MF57CPOWFNLPGGVD5NTJ7FDJA2VACTLFR7N';

const sourceKeypair = StellarSdk.Keypair.fromSecret(sourceSecretKey);
const sourcePublicKey = sourceKeypair.publicKey();
console.log('\nPublic Key derived = ');
console.log(sourcePublicKey);

const receiverPublicKey = 'GC6AESSU7M35TQEFUIVUW2G7375G5YRLIPIT7WDSJRLT5UMLI5P76F2S';

const server = new StellarSdk.Server('https://horizon-testnet.stellar.org');

StellarSdk.Network.useTestNetwork();

const account = await server.loadAccount(sourcePublicKey);

const fee = await server.fetchBaseFee();


const transaction = new StellarSdk.TransactionBuilder(account, { fee })
  .addOperation(StellarSdk.Operation.payment({
    destination: receiverPublicKey,
    asset: StellarSdk.Asset.native(),
    amount: '350.1234567',
  }))
  .setTimeout(30)
  .build();

transaction.sign(sourceKeypair);

console.log(transaction.toEnvelope().toXDR('base64'));

try {
  const transactionResult = await server.submitTransaction(transaction);
  console.log(JSON.stringify(transactionResult, null, 2));
  console.log('\nSuccess! View the transaction at: ');
  console.log(transactionResult._links.transaction.href);
} catch (e) {
  console.log('An error has occured:');
  console.log(e);
}

---

Answer 1

As others have described, you need to use await within an async function, so the following should work:

(Note the two comments...)

const StellarSdk = require('stellar-sdk');
const sourceSecretKey = 'SBHPB666WEISWVSIWWVBZ4RA3L7OXP53HJNT66UEJJSIERIBH2LCZSVS';
const sourceKeypair = StellarSdk.Keypair.fromSecret(sourceSecretKey);
const sourcePublicKey = sourceKeypair.publicKey();
const receiverPublicKey = 'GADJ4AWIARPTSUEN4GOXRFYSG45RMF665ZLRE6OSIDQ3DHFG44ZOFNLX';
const server = new StellarSdk.Server('https://horizon-testnet.stellar.org');
StellarSdk.Network.useTestNetwork();

// This line
const asyncScope = async function() {
    const account = await server.loadAccount(sourcePublicKey);

    const fee = await server.fetchBaseFee();

    const transaction = new StellarSdk.TransactionBuilder(account, { fee })
      .addOperation(StellarSdk.Operation.payment({
        destination: receiverPublicKey,
        asset: StellarSdk.Asset.native(),
        amount: '350.1234567',
      }))
      .setTimeout(30).build();

      transaction.sign(sourceKeypair);

    try {
      const transactionResult = await server.submitTransaction(transaction);
      console.log(JSON.stringify(transactionResult, null, 2));
      console.log('\nSuccess! View the transaction at: ');
      console.log(transactionResult._links.transaction.href);
    } catch (e) {
      console.log(e);
    }
}

// And this line
asyncScope();

Answer 2

The error itself contains all the information you need for the troubleshooting.

Probably you wrapped this code in some function (i.e. function testPayment() {...}). To make it work, add async keyword before the function declaration. Like async function testPayment() {...}.

Documentation on async/await usage in JS can be found here.

Answer 3

As the error says, you can't call await unless you're in an async function. If you literally copy/pasted the example into an editor and ran it, the issue is that you aren't in a function - you're at the top level. See. e.g. number 8 in this post (quoted below). The solution is to wrap the example code in an async function.

Sometimes, it’d be nice if you could use await at the top level of a module or script. Alas, it’s only available inside async functions. You therefore have several options. You can either create an async function main() and call it immediately afterwards:

async function main() {
    console.log(await asyncFunction());
}
main();

Or you can use an Immediately Invoked Async Function Expression:

(async function () {
    console.log(await asyncFunction());
})();

Another option is an Immediately Invoked Async Arrow Function:

(async () => {
    console.log(await asyncFunction());
})();

Answer 4

The test script requires some basic concepts with await/async, and is not going to work with direct copy-paste.

Start with this "create account" example to familiarize yourself with the syntax. Modify StellarSdk.Operation.&createAccount({~~}) to other operations like StellarSdk.Operation.payment({~~}) accordingly to test things out.