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

Question

I'm having array of objects where object looks like this (values change):

   {
     stats: {
        hp: 2,
        mp: 0,
        defence: 4,
        agility: 11,
        speed: 6,
        strength: 31
     }
   }

I want to sort them in descending order by speed doing:

  array.sort((a, b) => {
            return b.stats.speed - a.stats.speed
        })

However I'm getting this error and I can't really decipher whats going on:

TypeError: Cannot assign to read only property '2' of object '[object Array]'

What am I missing?

Edit: Array of object in redux store:

const enemyDefaultState = [
{
    name: 'European Boy1',
    stats: {
        hp: 2,
        mp: 0,
        defence: 4,
        agility: 11,
        speed: 6,
        strength: 31
    }
},
{
    name: 'European Boy2',
    stats: {
        hp: 2,
        mp: 0,
        defence: 4,
        agility: 4,
        speed: 2,
        strength: 31
    }
},
{
    name: 'European Boy3',
    stats: {
        hp: 2,
        mp: 0,
        defence: 4,
        agility: 7,
        speed: 7,
        strength: 31
    }
},

]

I import the array and assign it to the variable:

 let enemies = getState().enemy;
        if (enemies) {
            //sort by speed stat
            enemies.sort((a, b) => {
                return b.stats.speed - a.stats.speed
            })
        }

Answer 1

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)