Push last item to first in an array based on a count

Question

I have an array,

 var myArray = [ 1,2,3,4,5 ]

and variable count,

var count = 5

Pseudocode :

   if count = 1, output myArray = [5,1,2,3,4]  
   if count = 2, then myArray = [ 4,5,1,2,3]

and so on ..

How can I achieve this without using loops ?

Since you want to change every element in the array, *any* method will necessarily use a loop *somewhere*, even if abstracted behind some other iteration method — CertainPerformance, Dec 20 '18 at 12:49

score 5 · Answer 1 · answered Dec 20 '18 at 12:54

You could slice with a negative index from the end the array for the last part and the first part and concat a new array.

function move(array, i) {
    return array.slice(-i).concat(array.slice(0, -i));
}

var array = [1, 2, 3, 4, 5];

console.log(move(array, 1)); // [5, 1, 2, 3, 4].
console.log(move(array, 2)); // [4, 5, 1, 2, 3]

.as-console-wrapper { max-height: 100% !important; top: 0; }

score 2 · Answer 2 · answered Dec 20 '18 at 12:54

2

Use pop for removing last item of the array and unshift for adding it at the beginning of the arrray then

const count = 2;
const myArray = [ 1,2,3,4,5 ];
for (let i = 0; i < count; i++) {
  myArray.unshift(myArray.pop());
}
console.log(myArray);

answered Dec 20 '18 at 12:54

quirimmo

9,800
3
30
45

Push last item to first in an array based on a count

2 Answers2