Element.matches()

如果元素被指定的选择器字符串选择，Element.matches()  方法返回true; 否则返回false。

let result = element.matches(selectorString);

• result 的值为 true 或 false.
• selectorString 是个css选择器字符串.

<ul id="birds">
  <li>Orange-winged parrot</li>
  <li class="endangered">Philippine eagle</li>
  <li>Great white pelican</li>
</ul>

<script type="text/javascript">
  var birds = document.getElementsByTagName('li');

  for (var i = 0; i < birds.length; i++) {
    if (birds[i].matches('.endangered')) {
      console.log('The ' + birds[i].textContent + ' is endangered!');
    }
  }
</script>

<div id="foo">This is the element!</div>
  <script type="text/javascript">
    var el = document.getElementById("foo");
    if (el.mozMatchesSelector("div")) {
      alert("Match!");
    }
  </script>

会显示弹出框,因为"div"选择器可以选择到el元素.

SYNTAX_ERR

如果给定的css选择器无效. 在 Gecko 2.0之前,该方法会返回false,2.0之后,会直接抛出异常.

对于不支持 Element.matches() 或Element.matchesSelector()，但支持document.querySelectorAll()方法的浏览器，存在以下替代方案

if (!Element.prototype.matches) {
    Element.prototype.matches =
        Element.prototype.matchesSelector ||
        Element.prototype.mozMatchesSelector ||
        Element.prototype.msMatchesSelector ||
        Element.prototype.oMatchesSelector ||
        Element.prototype.webkitMatchesSelector ||
        function(s) {
            var matches = (this.document || this.ownerDocument).querySelectorAll(s),
                i = matches.length;
            while (--i >= 0 && matches.item(i) !== this) {}
            return i > -1;
        };
}

关于Polyfill的补充:

• Polyfill Wikipedia
• What are Polyfills in Javascript ?