Changing input border with Javascript

Question

What’s wrong? I need this effect to validate form.

var input = document.getElementByClass("dado");
input.style.border = "1px solid red";

Answer 1

You’re using the wrong getElementsByClassName. And the return is an array, so it must be accessed by the index:

var input = document.getElementsByClassName("dado");
input[0].style.border = "2px solid red";

<input class="dado" />