fix: ignore class names not suitable for selectors

refs #37

src/constants.js

@@ -18,6 +18,12 @@ export const INVALID_ID_RE = new RegExp([
   '^\\d', // begins with a number
 ].join('|'));
 
+// RegExp that will match invalid patterns that can be used in class attribute.
+export const INVALID_CLASS_RE = new RegExp([
+  '^$', // empty or not set
+  '^\\d', // begins with a number
+].join('|'));
+
 // Order in which a combined selector is constructed.
 export const SELECTOR_PATTERN = [
   'nthoftype',

src/selector-class.js

@@ -1,4 +1,5 @@
 import {sanitizeSelectorItem} from './utilities-selectors';
+import { INVALID_CLASS_RE } from './constants'
 
 /**
  * Get class selectors for an element.
@@ -9,6 +10,6 @@ export function getClassSelectors (element) {
   return (element.getAttribute('class') || '')
     .trim()
     .split(/\s+/)
-    .filter((item) => item !== '')
+    .filter((item) => !INVALID_CLASS_RE.test(item))
     .map((item) => `.${sanitizeSelectorItem(item)}`);
 }

test/selector-class.spec.js

@@ -56,4 +56,11 @@ describe('selector - class', function () {
     assert.include(result, '.aaa\\3A bbb');
   });
 
+  it('should ignore class names that start with a number', function () {
+    root.innerHTML = '<div class="1 1a a1"></div>'
+    const result = getClassSelectors(root.firstChild)
+    assert.lengthOf(result, 1)
+    assert.include(result, '.a1');
+  })
+
 });