Reverse filtered array Angular

Question

I have an array like ['a','b','c','d','e','f'] and I want to reverse only a part that I filter previously, for example I filter and I get ['c','d','e'] and I do reverse and the final result that I expected is ['a','b','e','d','c','f'].

I've tried to do array.slice().filter(condition).reverse(), and another solutions from stackoverflow but no one worked for me.

Any idea?

Answer 1

if you know the starting index and length of sub-array you want to reverse

const arr = ['a','b','c','d','e','f'];

function reverse(arr, i, j){
    while(i <j){
      const temp = arr[i]
      arr[i]=arr[j];
      arr[j]=temp;
      i++;
      j--;
    }
   return arr;
}

const result = reverse(arr, 2, 4) 
console.log(result)  //  ["a", "b", "e", "d", "c", "f"]

the code above will solve your problem in time complexity of O(n)