JSFiddle - React, Tailwind, and code Playground

JavaScript

function nome(str) {
    var arr = str.split(' ');
    if (arr[1][0].toUpperCase() != arr[1][0]) arr.splice(1, 1);
    return arr.slice(0, 2).join(' ');
}

alert(nome('Renan Rodrigues Moraes'));
alert(nome('Renan de Rodrigues Moraes'));