JSFiddle - React, Tailwind, and code Playground

JavaScript

function nome(str) {
    var arr = str.split(' ');
	var keep = arr[1][0].toUpperCase() != arr[1][0];
    return arr.slice(0, keep ? 3 : 2).join(' ');
}

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