Fix global leaks detected by mocha

Fix globals leaked in stringUtils, isJson and static/nav.html.

lib/stringUtils.js

@@ -3,8 +3,7 @@ function hashCode(string){
 	var hash = 0;
 	if (string.length == 0) return hash;
 	for (let i = 0; i < string.length; i++) {
-		char = string.charCodeAt(i);
-		hash = ((hash << 5) - hash) + char;
+		hash = ((hash << 5) - hash) + string.charCodeAt(i);
 		hash = hash & hash; // Convert to 32bit integer
 	}
 	return hash;