JSFiddle - React, Tailwind, and code Playground

JavaScript

function reverse(input, output) {
    output = output || '';
    if (input.length > 0) {
        output = output.concat(input[input.length -1]);
        return reverse(input.substr(0, input.length - 1), output);
    }
    return output;
}

console.log(reverse('Obama'));