JSFiddle - React, Tailwind, and code Playground

JavaScript

Date.prototype.sumarDias=function(dias){
    if (!isNaN(dias))
    {
        dias=parseInt(dias);
        this.setDate(this.getDate()+dias);
    }
    return this;
}

var hoy=new Date();
alert(hoy);
hoy.sumarDias(1);
alert(hoy);