Vanilla JavaScript addClass

addClass.js

function addClass(elements, myClass) {
  // if there are no elements, we're done
  if (!elements) {
    return;
  }

  // if we have a selector, get the chosen elements
  if (typeof elements === "string") {
    elements = document.querySelectorAll(elements);
  }

  // if we have a single DOM element, make it an array to simplify behavior
  else if (elements.tagName) {
    elements = [elements];
  }

  // add class to all chosen elements
  for (var i = 0; i < elements.length; i++) {
    // if class is not already found
    if ((" " + elements[i].className + " ").indexOf(" " + myClass + " ") < 0) {
      // add class
      elements[i].className += " " + myClass;
    }
  }
}

/*

• <script src="addClass.js"></script>
• <script>
• addClass('#iddiv','highlight');
• addClass('.classdiv','red');
• </script>
• does not add classes to HTML elements loaded via ajax
  */