JavaScript Reversing arrays


Example

.reverse is used to reverse the order of items inside an array.

Example for .reverse:

[1, 2, 3, 4].reverse();

Results in:

[4, 3, 2, 1]

Note: Please note that .reverse(Array.prototype.reverse) will reverse the array in place. Instead of returning a reversed copy, it will return the same array, reversed.

var arr1 = [11, 22, 33];
var arr2 = arr1.reverse();
console.log(arr2); // [33, 22, 11]
console.log(arr1); // [33, 22, 11]

You can also reverse an array 'deeply' by:

function deepReverse(arr) {
  arr.reverse().forEach(elem => {
    if(Array.isArray(elem)) {
      deepReverse(elem);
    }
  });
  return arr;
}

Example for deepReverse:

var arr = [1, 2, 3, [1, 2, 3, ['a', 'b', 'c']]];

deepReverse(arr);

Results in:

arr // -> [[['c','b','a'], 3, 2, 1], 3, 2, 1]