protocol/packages/website/md/docs/0xjs/1.0.1/async.md

0x packages are promise-based libraries. This means that whenever an asynchronous call is required, the library method will return a native Javascript promise. You can therefore choose between using promise or async/await syntax when calling our async methods.

Async/await syntax (recommended):

try {
    const signature = await signatureUtils.ecSignOrderHashAsync(
        providerEngine,
        orderHashHex,
        maker,
        SignerType.Default,
    );
} catch (error) {
    console.log('Caught error: ', error);
}

Promise syntax:

signatureUtils
    .ecSignOrderHashAsync(providerEngine, orderHashHex, maker, SignerType.Default)
    .then(function(signature) {
        console.log(signature);
    })
    .catch(function(error) {
        console.log('Caught error: ', error);
    });

As is the convention with promise-based libraries, if an error occurs, it is thrown. It is the callers responsibility to catch thrown errors and to handle them appropriately.