I am trying to write a function that removes all the elements from an array called selectedItems.
It looks like this:
const selectNone = (e: any) => {
let selectedItemsCopy = selectedItems;
selectedItemsCopy = []
setState(
{
...state,
areAllSelected: false,
isChecked: false,
selectedItems: selectedItemsCopy
}
);
}
but in setState, selectedItems does not get updated to the empty copy of the array. What am I doing wrong?
The problem that you have is, that you are actually mutating state, which is basically prohibited in React. In this case, it's very simple to solve, just put the [] inside the setState directly, without any variables:
const selectNone = (e: any) => {
setState(
{
...state,
areAllSelected: false,
isChecked: false,
selectedItems: []
}
);
}
The method you are using to make a copy of the array, doesn't actually copy the array and instead just creates a reference to the original (that's how JS works). In order to make a proper copy (for example to be able to make modifications, not just clear the array), you should use Array.from().
Here's an example
const selectNone = (e: any) => {
let selectedItemsCopy = Array.from(selectedItems);
selectedItemsCopy[x] = changedValue;
setState(
{
...state,
areAllSelected: false,
isChecked: false,
selectedItems: selectedItemsCopy
}
);
}
[] is what I had initially, which also didn't work!