Get elements by attribute when querySelectorAll is not available without using libraries?

Question

How can you do the equivalent to

document.querySelectorAll(\'[data-foo]\')

where query

Answer 1

A little modification on @kevinfahy 's answer, to allow getting the attribute by value if needed:

function getElementsByAttributeValue(attribute, value){
  var matchingElements = [];
  var allElements = document.getElementsByTagName('*');
  for (var i = 0, n = allElements.length; i < n; i++) {
    if (allElements[i].getAttribute(attribute) !== null) {
      if (!value || allElements[i].getAttribute(attribute) == value)
        matchingElements.push(allElements[i]);
    }
  }
  return matchingElements;
}