getAncestorElementByTagName.js : 対象の tagName を持つ祖先要素ノードを返す。存在しなければ null を返す。

getAncestorElementByTagName.js

/**
 * getAncestorElementByTagName.js
 *
 * @version 1.0
 * @author think49
 */


/**
 * get Ancestor Element by tagName.
 * @function
 * @param {Object}  node    DOM Node.
 * @param {String}  tagName Tag Name.
 * @returns Ancestor element node. If a target node is not found, return null.
 * @type {Object}, {Boolean}
 */
function getAncestorElementByTagName (node, tagName) {
  if (typeof node !== 'object' || !node) {
    return null;
  }

  tagName = (tagName + '').toLowerCase();

  while (node && node.parentNode) {
    node = node.parentNode;

    if (node.tagName && node.tagName.toLowerCase() === tagName) {
      break;
    }
  }

  return node;
}