2👍
✅
Array.prototype.sort
mutates the array that you call it on.
Assuming that cmp.getPurposesAllowed()
returns a reference to an array in your vuex store, your are mutating that array from the store, just like the error message says.
Solution: Make a shallow copy of the array before:
let purposeArrayZ = cmp.getPurposesAllowed().slice();
Source:stackexchange.com