如何检查 svg 路径是否具有与数组中的值匹配的类，如果是，则添加新类

I have an array and some svg path elements (I am using leaflet map). I need to check if the class of a path matches one of the values in my array and if so add a class fadeIn to it.

var foundNations = ["usa", "France", "Italy"];
document.querySelectorAll('path').forEach(path => {
  if (foundNations.includes(path.className)) {
   path.className.add('fadeIn');
    console.log(path.className);
  }
});
(function($) {
    var map = L.map('map').setView([45.4655171, 12.7700794], 2);
    map.fitWorld().zoomIn();
    L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4NXVycTA2emYycXBndHRqcmZ3N3gifQ.rJcFIG214AriISLbB6B5aw', {
      attribution: 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' + '<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' + 'Imagery © <a href="http://mapbox.com">Mapbox</a>',
      id: 'mapbox.light'
    }).addTo(map);

    var mapHalfHeight = map.getSize().y / 2,
    container = map.zoomControl.getContainer(),
    containerHalfHeight = parseInt(container.offsetHeight / 2),
    containerTop = mapHalfHeight - containerHalfHeight + 'px';

    container.style.position = 'absolute';
    container.style.top = containerTop;
    map.scrollWheelZoom.disable();
    var southWest = L.latLng(-89.98155760646617, -180),
    northEast = L.latLng(89.99346179538875, 180);
    var bounds = L.latLngBounds(southWest, northEast);
    map.setMaxBounds(bounds);
    map.on('drag', function() {
      map.panInsideBounds(bounds, { animate: false });
    });

  // get color depending on population density value
    function getColor(d) {
      return d > 1000 ? '#800026' :
        d > 500  ? '#BD0026' :
        d > 200  ? '#E31A1C' :
        d > 100  ? '#FC4E2A' :
        d > 50   ? '#FD8D3C' :
        d > 20   ? '#FEB24C' :
        d > 10   ? '#FED976' :
              '#FFEDA0';
    }

    function style(feature) {
      return {
        weight: 1,
        opacity: 1,
        color: '#ffffff',
        dashArray: '',
        fillOpacity: 0,
        fillColor : '#FF0080',
        className: feature.properties.name
      };
    }

    var geojson;

    function selectNation(e) {

    }


   function onEachFeature(feature, layer) {
      layer.on({
        click: selectNation
      });
    }

    geojson = L.geoJson(statesData, {
      style: style,
      onEachFeature: onEachFeature
    }).addTo(map);
})( jQuery );

#map {
  width: 100vw;
  height: 100vh;
}

.fadeIn {
  fill: red;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://unpkg.com/leaflet@1.3.1/dist/leaflet.js"></script>
<link href="https://unpkg.com/leaflet@1.3.1/dist/leaflet.css" rel="stylesheet"/>
<script src="https://www.jikupin.com/world.json"></script>

<div id='map'></div>

推荐答案

你的错误很微妙.您从 Strings:

Your bug is subtle. You are starting with an Array of Strings:

var nationList = ["usa", "france", "italy"];

然后你调用 String.prototype.includes，将 path.className 作为参数传递.

Then you're calling String.prototype.includes, passing path.className as an argument.

if (foundNations.includes(path.className)) { path.classList.add('fadeIn')

在那里，您隐含地假设 path.className 是一个String.但是，令人惊讶的是，它不是 String，而是 SVGAnimatedString!

In there, you're implicitly assuming that path.className is a String. But, surprise surprise, it's not a String, it's a SVGAnimatedString!

console.log(path.className)
> [object SVGAnimatedString] {
   animVal: "germany",
   baseVal: "germany"
  }

是的，在某些极端情况下，SVG 元素的类名可以在动画期间进行修改.

Yes, class names for SVG elements can be modified during animations in some edge cases.