Use JSDoc @callback for nodeListForEach()

src/govuk/common.mjs

@@ -8,7 +8,7 @@ import './vendor/polyfills/Element/prototype/closest.mjs'
  * See: https://github.com/imagitama/nodelist-foreach-polyfill
  *
  * @param {NodeListOf<Element>} nodes - NodeList from querySelectorAll()
- * @param {(value: Element, key: number, parent: NodeListOf<Element>) => void} callback - Callback function to run for each node
+ * @param {nodeListIterator} callback - Callback function to run for each node
  * @returns {void}
  */
 export function nodeListForEach (nodes, callback) {
@@ -213,3 +213,11 @@ export function closestAttributeValue ($element, attributeName) {
     return closestElementWithAttribute.getAttribute(attributeName)
   }
 }
+
+/**
+ * @callback nodeListIterator
+ * @param {Element} value - The current node being iterated on
+ * @param {number} index - The current index in the iteration
+ * @param {NodeListOf<Element>} nodes - NodeList from querySelectorAll()
+ * @returns {void}
+ */