Uncaught TypeError: Cannot add property 0, object is not extensible at Array.push

Question

I am getting this error when fetching data from firebase and pushing the data into an array. Here I define a temp array when I am pushing data inside firebase onValue into this temp array I am getting this error Uncaught TypeError: Cannot add property 0, object is not extensible at Array.push. Here is my code

function Room() {
const [textInput, setTextInput] = useState('');
const temp = [];

const handleTextInputChange = (event) => {
    setTextInput(event.target.value);
};

const handleSubmit = () => {
    console.log('here goes');
    if (textInput !== '') {
        const refer = ref(database, 'rooms/');
        push(refer, textInput).then(() => {
            setTextInput('');
            toast.success('Added Successfully!');
        });
    }
};

useEffect(() => {
    const refer = ref(database, 'rooms/');
    onValue(refer, (snap) => {
        snap.forEach((child) => {
            console.log(child.val() + child.key);
            // I am getting error in this line
            temp.push({ id: child.key, firstName: child.val() });
        });
    });
}, []);

return (
  <div>
    <Grid item xs={12}>
                <SubCard title="Room List">
                    <div style={{ height: 400, width: '100%' }}>
                        <DataGrid
                            rows={temp}
                            columns={columns}
                            pageSize={5}
                            rowsPerPageOptions={[5]}
                            components={{
                                Toolbar: CustomToolbar
                            }}
                        />
                    </div>
                </SubCard>
            </Grid>
  </div>
)

Answer 1

The error you're getting is what you get when you try to push to a frozen array:

const temp = Object.freeze([]);
temp.push(42);

You've shown that you're passing the array to DataGrid as rows. Apparently, DataGrid freezes the array, presumably because it needs to know that the contents of it don't change.

If you want to change those contents, you'll need to store temp in state and re-render after adding to it; see *** comments (I've also renamed temp to dataGridRows):

function Room() {
    const [textInput, setTextInput] = useState('');
    // *** Store it in state
    const [dataGridRows, setDataGridRows] = useState([]);

    const handleTextInputChange = (event) => {
        setTextInput(event.target.value);
    };

    const handleSubmit = () => {
        console.log('here goes');
        if (textInput !== '') {
            const refer = ref(database, 'rooms/');
            push(refer, textInput).then(() => {
                setTextInput('');
                toast.success('Added Successfully!');
            });
        }
    };

    useEffect(() => {
        const refer = ref(database, 'rooms/');
        onValue(refer, (snap) => {
            snap.forEach((child) => {
                console.log(child.val() + child.key);
                // *** Add to it in state; this will cause a re-render
                // so DataGrid picks up the change
                setDataGridRows(dataGridRows => [...dataGridRows, { id: child.key, firstName: child.val() }];
            });
        });
    }, []);

    return (
        <div>
            <Grid item xs={12}>
                <SubCard title="Room List">
                    <div style={{ height: 400, width: '100%' }}>
                        <DataGrid
                            rows={dataGridRows}
                            columns={columns}
                            pageSize={5}
                            rowsPerPageOptions={[5]}
                            components={{
                                Toolbar: CustomToolbar
                            }}
                        />
                    </div>
                </SubCard>
            </Grid>
        </div>
    )
}