use a regexp to make sure user only changes the first line

challenges/02-javascript-algorithms-and-data-structures/basic-javascript.json

@@ -393,8 +393,7 @@
       ],
       "tests": [
         "assert(difference === 12, 'message: Make the variable <code>difference</code> equal 12.');",
-        "assert((code).match(/difference/g).length === 1,'message: Only change the first line');",
-        "assert(/\\d+\\s*-\\s*\\d+/.test(code),'message: Use the <code>-</code> operator');"
+        "assert(/var\\s*difference\\s*=\\s*45\\s*-\\s*33;?/.test(code),'message: Only subtract one number from 45.');"
       ],
       "type": "waypoint",
       "challengeType": 1,