document.getElementbyId is not finding element added by a fetch-CodePudding

I have a chat program that adds an element to the dom when messaged. This element adds properly, but when I go to query it from the dom it shows as null. I do a fetch to the server just before, but it has an await to slow it down. Any ideas?

Here is my javascript code

        socket.on('receive_message', async function(data) {
            let messaged_user_li = document.getElementById('messaged_user_li' data['from_user']);
            console.log('messaged_user_li: ' messaged_user_li)
            if (messaged_user_li == null) {
                console.log('if fired')
                await fetch('/get_messaged_user/' data['from_user']).then((response) => {
                    response.json().then((data2) => {
                        loadMessagedUser(data2[0].id, data2[0].avatar, data2[0].username, data2[0].last_seen);
                    });
                });
                console.log(data['from_user'])
                messaged_user_li = document.getElementById('messaged_user_li' data['from_user']);
                //despite this element being added this log shows nulls which causes issues later on in the code.
                console.log('messaged_user_li: ' messaged_user_li)     
            }
            
            let message_user = document.getElementById('message_user' data['from_user']);

            let message_target = document.getElementById("message_target" data['from_user']);
            if (messaged_user_li.classList.contains('active') == false) {
                messaged_user_li.classList.add('flash-message');
            }
            if (message_user != null) {
                data = `
                <li >
                    <div >
                        <span >just now</span>
                    </div>
                    <div >` data['message'] `</div>
                </li>`;
                message_target.innerHTML  = data;
                //Move scroller to bottom when message received
                myDiv = message_user.querySelector(".chat-history");
                myDiv.scrollTop = myDiv.scrollHeight;
            }
        });

CodePudding user response：

You are only waiting for this promise to complete:

await fetch('/get_messaged_user/' data['from_user']).then((response) => {
    // ...
});

Not this one inside the callback:

response.json().then((data2) => {
    loadMessagedUser(data2[0].id, data2[0].avatar, data2[0].username, data2[0].last_seen);
});

Which is why your code continues executing and trying to get the added element (which hasn't been added yet).

To solve this, you could chain the then calls:

await fetch('/get_messaged_user/' data['from_user'])
    .then((response) => response.json())
    .then((data2) => loadMessagedUser(data2[0].id, data2[0].avatar, data2[0].username, data2[0].last_seen));

Or use await again:

const response = await fetch('/get_messaged_user/' data['from_user']);
const data2 = await response.json();
loadMessagedUser(data2[0].id, data2[0].avatar, data2[0].username, data2[0].last_seen);