how to update nested useState?

Question

Hey there im having an issue on updating the useState. I saw some example but when trying to implement it it does not work.. Anyone can give me a hand on sorting this little issue?

this is the original state and i need to update labels

        setChartData({
            labels: [ ],
            datasets:[
            {
                label:'Sales',
                data:[ //values for population num
                    
                ],
                backgroundColor:[
                    'rgba(255, 99, 132, 0.6)',
                    'rgba(54, 162, 235, 0.6)',
                    'rgba(255, 206, 86, 0.6)',
                    'rgba(75, 192, 192, 0.6)',
                    'rgba(153, 102, 255, 0.6)',
                    'rgba(255, 159, 64, 0.6)',
                    'rgba(255, 99, 132, 0.6)'
                ]
            }
            ]
        })

this is the array im trying to assign to labels array

        for (let y = 0; y < weeks.length; y++) {
            setChartData(prevState => ({
                ...prevState,
                labels: {
                    ...prevState.labels,
                    weeks[y]
                }
            }))
        }

Answer 1

Oops: You've used the wrong braces in your loop! Try this:

for (let y = 0; y < weeks.length; y++) {
  setChartData((prevState) => ({
    ...prevState,
    labels: /* { */ [
      ...prevState.labels,
      weeks[y]
    ] /* } */
  }));
}

You were replacing your labels array with an object using an invalid syntax, this is probably what you meant to do.

Answer 2

Try without taking the prevState as an argument in the callback, like this:

for (let y = 0; y < weeks.length; y++) {
            setChartData(() => ({
                ...chartData //or whatever you called your state variable.
                labels: {
                    ...chartData.labels,
                    weeks[y]
                }
            }))
        }