如何根据最高z索引获取元素属性开发者社区

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function findHighestZIndex(elem)
  var elems = document.getElementsByClassName(elem);
  var highest = 0;
  for (var i = 0; i < elems.length; i++)
    var id = document.getElementsByClassName(elem); 
    id.getAttribute("id");
console.log(id);
    var zindex=document.defaultView.getComputedStyle(elems[i],null).getPropertyValue("z-index");
    var ElementDisplay = document.defaultView.getComputedStyle(elems[i],null).getPropertyValue("display");
    if ((zindex > highest) && (zindex != 'auto') && (ElementDisplay == 'block'))
      highest = zindex;
    }

function getHighest(selector) {
  // Return the element that matches selector having the largest z index
  return Array.from(document.querySelectorAll(selector)).reduce((a, b) => getZIndex(a) >= getZIndex(b) ? a : b);
function getZIndex(el) {
  // Return the z-index of el, or 0 if none is set.
  return parseInt(getCssProperty(el, "z-index")) || 0;
function getCssProperty(el, prop) {
  // Return the computed value of the css property prop for the element el
  return document.defaultView.getComputedStyle(el, null).getPropertyValue(prop);
// -------------------------------------------------------------------------
// additional code for demo below
// -------------------------------------------------------------------------
function updateHighest() {
  let highest = getHighest(".box");
  document.querySelector("#highest").textContent = `#${highest.id} (${getZIndex(highest)})`;
  document.querySelector("#highest").style.color = getCssProperty(highest, "background-color");
function setContentToZIndex(el) {
  el.textContent = getZIndex(el);
Array.from(document.querySelectorAll(".box")).forEach(b => {
  b.onclick = () => {
    b.style.zIndex = getZIndex(b) + 1;
    setContentToZIndex(b);
    updateHighest();
  setContentToZIndex(b);
  updateHighest();
});

.box {
  width: 100px;
  height: 100px;
  display: block;
  background: grey;
  position: absolute;
  color: white;
  font-size: 2rem;
  text-align: center;
  line-height: 100px;
  user-select: none;
  font-family: sans-serif;
#b1 {
  background: #ff268a;
  left: 0px;
  top: 0px;
#b2 {
  background: #242792;
  left: 50px;
  top: 50px;
#b3 {
  background: #0ac3d6;
  left: 25px;
  top: 75px;
  margin-left: 200px;
  font-family: sans-serif;
  font-size: 1.2rem;
}

<div class="box" id="b1"></div>
<div class="box" id="b2"></div>
<div class="box" id="b3"></div>
<p>highest z-index: <span id="highest"></span></p>

var elems = document.getElementsByClassName(elem);
var highest = 0;
  for (var i = 0; i < elems.length; i++)
      //This is all wrong here, commenting it out
      //var id = document.getElementsByClassName(elem); //You already have this collection
      //id.getAttribute("id"); //The above returns a collection so this would fail, you'd need to use an index of the collection
      //console.log(id);
      //You already have the elements you want, just use the i index to grab the element
      //and it's id
      console.log(elems[i].id);

 function isNumeric(val) {
return !isNaN(parseFloat(val)) && isFinite(val);
function findHighestZIndex(className) {
let queryObject = document.getElementsByClassName(className);
let childNodes = Object.keys(queryObject).map(key => queryObject[key]);
let highest = 0;
var highestElem;
childNodes.forEach((node) => {
  // Get the calculated CSS z-index value.
  let cssStyles = document.defaultView.getComputedStyle(node);
  let cssZIndex = cssStyles.getPropertyValue('z-index');
  // Get any inline z-index value.
  let inlineZIndex = node.style.zIndex;
  // Coerce the values as integers for comparison.
  cssZIndex = isNumeric(cssZIndex) ? parseInt(cssZIndex, 10) : 0;
  inlineZIndex = isNumeric(inlineZIndex) ? parseInt(inlineZIndex, 10) : 0;
  // Take the highest z-index for this element, whether inline or from CSS.
  let currentZIndex = cssZIndex > inlineZIndex ? cssZIndex : inlineZIndex;
  if ((currentZIndex > highest)) {
    highest = currentZIndex;
    highestElem = node;
var obj = {highestZIndex: highest, elem: highestElem};
 return obj;
}

<!DOCTYPE html>
</head>
<div class="test" style="z-index: 100;" id="x">1</div>
<div class="test" style="z-index: 10;">2</div>
<div class='test' id="test">3</div>
<script>
function isNumeric(val) {
    return !isNaN(parseFloat(val)) && isFinite(val);
function findHighestZIndex(className) {
    let queryObject = document.getElementsByClassName(className);
    let childNodes = Object.keys(queryObject).map(key => queryObject[key]);
    let highest = 0;
    var highestElem;
    childNodes.forEach((node) => {
      // Get the calculated CSS z-index value.
      let cssStyles = document.defaultView.getComputedStyle(node);
      let cssZIndex = cssStyles.getPropertyValue('z-index');
      // Get any inline z-index value.
      let inlineZIndex = node.style.zIndex;
      // Coerce the values as integers for comparison.
      cssZIndex = isNumeric(cssZIndex) ? parseInt(cssZIndex, 10) : 0;
      inlineZIndex = isNumeric(inlineZIndex) ? parseInt(inlineZIndex, 10) : 0;
      // Take the highest z-index for this element, whether inline or from CSS.
      let currentZIndex = cssZIndex > inlineZIndex ? cssZIndex : inlineZIndex;
      if ((currentZIndex > highest)) {
        highest = currentZIndex;
        highestElem = node;
    var obj = {highestZIndex: highest, elem: highestElem};
    return obj;
 console.log(findHighestZIndex('test').elem.id);

回答 3

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