JSFiddle - React, Tailwind, and code Playground

JavaScript

var pairSwapRecursive = function(arr) {
    if (arr.length < 2) {
        return arr;
    }
    
    return [arr[1], arr[0]].concat(pairSwapRecursive(arr.slice(2)));
};

console.log(pairSwapRecursive([1,2,3,4,5]));