[removeElementsByAttr] fix removing elements when class is empty

Ref https://github.com/svg/svgo/issues/937

Regexp didn't not cover the case when class list is empty.

plugins/removeElementsByAttr.js

@@ -51,8 +51,6 @@ exports.params = {
  * @author Eli Dupuis (@elidupuis)
  */
 exports.fn = function(item, params) {
-    var elemId, elemClass;
-
   // wrap params in an array if not already
   ['id', 'class'].forEach(function(key) {
     if (!Array.isArray(params[key])) {
@@ -66,15 +64,15 @@ exports.fn = function(item, params) {
   }
 
   // remove element if it's `id` matches configured `id` params
-    elemId = item.attr('id');
-    if (elemId) {
-        return params.id.indexOf(elemId.value) === -1;
+  const elemId = item.attr('id');
+  if (elemId && params.id.length !== 0) {
+    return params.id.includes(elemId.value) === false;
   }
 
   // remove element if it's `class` contains any of the configured `class` params
-    elemClass = item.attr('class');
-    if (elemClass) {
-        var hasClassRegex = new RegExp(params.class.join('|'));
-        return !hasClassRegex.test(elemClass.value);
+  const elemClass = item.attr('class');
+  if (elemClass && params.class.length !== 0) {
+    const classList = elemClass.value.split(' ');
+    return params.class.some(item => classList.includes(item)) === false;
   }
 };

test/plugins/removeElementsByAttr.07.svg

@@ -0,0 +1,9 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="19" height="19" viewBox="0 0 19 19">
+    <rect class="some-class" width="19" height="19"/>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" width="19" height="19" viewBox="0 0 19 19">
+    <rect class="some-class" width="19" height="19"/>
+</svg>