Trocar "input" de acordo com o "option" escolhido

by Jairo Fontes

HTML

<form>
    <select name="pessoa" id="pessoa">
        <option value="Não especificado">*Tipo de Pessoa</option>
        <option value="Física">Física</option>
        <option value="Jurídica">Jurídica</option>
    </select>
    <input name="nome" id="nome" placeholder="Nome Completo" />
    <input name="icpf" id="icpf" placeholder="CPF" />
    <input name="icnpj" id="icnpj" placeholder="CNPJ" />
</form>

CSS

input {
    border: 1px solid #CCCCCC;
    box-shadow: 2px 2px 4px #EEEEEE inset;
    color: #999999;
    font-size: 18px;
    font-weight: 300;
    margin: 0 0 10px;
    padding: 10px;
    position: relative;
    width: 97%;
    font-family:'Roboto'
}
input:focus {
    border-color: #CCC;
    -webkit-box-shadow: none;
    -moz-box-shadow: none;
    -o-box-shadow: none;
    box-shadow: none;
    background-color: #F3F3F3;
}
select {
    border: 1px solid #CCCCCC;
    box-shadow: 2px 2px 4px #EEEEEE inset;
    color: #999999;
    font-size: 18px;
    font-weight: 300;
    margin: 0 0 10px;
    padding: 10px;
    position: relative;
    width: 99.7%;
    font-family:'Roboto';
    option {
        color: #999999;
        font-size: 18px;
        font-weight: 300;
        padding-left: 10px;
        position: relative;
        font-family:'Roboto';
    }
}

JavaScript

// select
var select = document.getElementById("pessoa");
// input
var input = document.getElementById("nome");

// quando o select muda
select.onchange = function () {
    var valor = select.options[select.selectedIndex].value;
    input.value = valor == 'Jurídica' ? '* Nome de sua Empresa' : '* Nome Completo';
}