I am learning React for a project at work and currently really having trouble getting the hang of the asynchronous model.

Here is the component I’m working on:

const Customers = () => {
    const [logos, setLogos] = useState([]);
    const [customers, setCustomers] = useState([]);
    const [titlePrompt, setTitlePrompt] = useState([]);
    const navigate = useNavigate();

    useEffect(() => {
        // create a customer client object 
        const client = new Client();

        // query for the customer list and save name and token
        if (customers.length === 0) {
            client.get_customers().then((res) => {
                const customer_info = res.map(customer => {
                    return {
                        'name': customer.customer_name,
                        'token': customer.mqtt_customer_token
                    }
                });
                setCustomers(customer_info);
            });
        }

        if (customers.length > 0) {
            const fetched_logos = [];
            for (let i = 0; i < customers.length; i++) {
                client.get_site_by_type(customers[i].token, 1).then((res) => {
                    const new_logo = {
                        [customers[i].name]: res.logo 
                    };
                    fetched_logos.push(new_logo);
                });
            }
            setLogos(fetched_logos);
        }

        setTitlePrompt("Select A Customer Shown Below");
    }, [customers, logos]);

    /**
     * button handler to transition to a dataframe view of the chosen customer via token
     * @param {defining} token 
     */
    const onButtonClick = (token) => {
        navigate('/dataframe', { state: { token } });
    };

    return (
        <div className={'mainContainer'}>
            <div className={'contentContainer'}>
                <div className={'titleContainer'}>
                    <div>{titlePrompt}</div>
                </div>
                <br/>
                <ImageList cols={4}>
                    {customers.map(customer => (
                        <ImageListItem key={customer.name}>
                            <img alt={customer.name} src={`data:image/png;base64,${logos[customer.name]}`}></img>
                        </ImageListItem>
                    ))}
                </ImageList>
            </div>
        </div>
    );
};

export default Customers;

What I’m trying to do is fetch customer information such as name and logo and display them in an ImageList.

The problem is, first I have to fetch the name and token (used for subsequent API calls) for each customer from one database, then I need to fetch the logos one by one since they all reside in specific customer databases. I want to render the component with only the img component’s alt text and then populate the images as they come in. I just can’t figure out how to synchronize this correctly inside useEffect. I also don’t know if using the if statements to control what gets executed during subsequent useEffect calls is the right thing to do or just hacky.

I tried chaining .then but the setState calls are asynchronous so it leads to race conditions and doesn’t work.

Thank you for reading.