🐛 Fixed root option trailing slash issue

src/url/root.js

@@ -2,14 +2,14 @@
  * Root Prefix Transform.
  */
 
-import { isString } from '../util';
+import { isString, trimEnd } from '../util';
 
 export default function (options, next) {
 
     var url = next(options);
 
-    if (isString(options.root) && !url.match(/^(https?:)?\//)) {
-        url = options.root + '/' + url;
+    if (isString(options.root) && !/^(https?:)?\//.test(url)) {
+        url = trimEnd(options.root, '/') + '/' + url;
     }
 
     return url;

src/util.js

@@ -33,6 +33,16 @@ export function trim(str) {
     return str ? str.replace(/^\s*|\s*$/g, '') : '';
 }
 
+export function trimEnd(string, chars) {
+    if (string && chars === undefined) {
+        return string.replace(/\s+$/, '');
+    }
+    if (!string || !chars) {
+        return string;
+    }
+    return string.replace(new RegExp(`[${chars}]+$`), '');
+}
+
 export function toLower(str) {
     return str ? str.toLowerCase() : '';
 }