Edit in JSFiddle

var div = document.getElementsByTagName("div")[0],
    spans = [],
    i = 0;

if (div.hasChildNodes()){
    var children = x = div.childNodes,
        total = children.length;
    
  for (i = 0; i < total; i++)
    if (children[i].nodeName === "SPAN")
      spans.push(children[i]);
}

console.log(spans); //Muestra [span, span, span]

<div>
    <p></p>
    <span></span>
    <input />
    <span></span>
    <select></select>
    <article></article>
    <span></span>
</div>