[Javascript] Promise-based functions should not throw exceptions

Source

You can also start a chain of then() method calls via Promise.resolve() and execute the synchronous code inside a callback:

    function asyncFunc() {
        return Promise.resolve()
        .then(() => {
            doSomethingSync();
            return doSomethingAsync();
        })
        .then(result => {
            ···
        });
    }

An alternative is to start the Promise chain via the Promise constructor:

    function asyncFunc() {
        return new Promise((resolve, reject) => {
            doSomethingSync();
            resolve(doSomethingAsync());
        })
        .then(result => {
            ···
        });
    }

This approach saves you a tick (the synchronous code is executed right away), but it makes your code less regular.