Error while sorting array of objects Cannot assign to read only property '2' of object '[object Array]'

Because the array is frozen in strict mode, you'll need to copy the array before sorting it:

array = array.slice().sort((a, b) => b.stats.speed - a.stats.speed)

The reason as Patrick stated is because the array is frozen. So any method of copying the array will work such as the one he suggests.

array = array.slice().sort((a, b) => b.stats.speed - a.stats.speed)

I just want to add that the reason the array is frozen in your case is because your using the array as props from the redux store and props in React are immutable hence your not being able to mutate the array.

The array is frozen to prevent mutation of the redux state. You use react cloneElement(): https://reactjs.org/docs/react-api.html#cloneelement

[...enemies].sort((a, b) => {
                return b.stats.speed - a.stats.speed
            })