sort and splice

These methods change the array in place — unless you copy first.

sort and splice mutate. Prefer [...arr].sort(...) or arr.slice() when you must keep the original. Modern engines also have toSorted / toReversed; this lab teaches the copy-first pattern.

Working array A (may mutate)


        

        

          
Working array B / copy result

          

        

      

      
Compare mutate vs copy-first.

    


    

      
Important JavaScript

      
const scores = [30, 10, 20];

scores.sort((a, b) => a - b);
// scores is now [10, 20, 30] — mutated

const safe = [...scores].sort((a, b) => b - a);
// new sorted array; original left alone if you copied first

const names = ["Ava", "Ben", "Cara"];
names.splice(1, 1, "Blair");
// removed 1 item at index 1, inserted "Blair"

const next = names.slice();
next.splice(0, 1);
// mutate only the copy