fix: wrapper.attributes() method (#265)

Author: tianyong90

src/wrappers/wrapper.js

@@ -37,11 +37,12 @@ export default class Wrapper implements BaseWrapper {
    * Returns an Object containing all the attribute/value pairs on the element.
    */
   attributes (): { [name: string]: string } {
-    const attributes = [...this.element.attributes] // NameNodeMap is not iterable
+    const attributes = this.element.attributes
     const attributeMap = {}
-    attributes.forEach((att) => {
+    for (let i = 0; i < attributes.length; i++) {
+      const att = attributes.item(i)
       attributeMap[att.localName] = att.value
-    })
+    }
     return attributeMap
   }