Improve JS detection

src/drivers/npm/driver.js

@@ -65,16 +65,25 @@ function getJs(page, technologies = Wappalyzer.technologies) {
         chains.forEach((chain) => {
           chain = chain.replace(/\[([^\]]+)\]/g, '.$1')
 
-          const value = chain
+          const parts = chain.split('.')
-            .split('.')
+
-            .reduce(
+          const root = /^[a-z_$][a-z0-9_$]*$/i.test(parts[0])
+            ? // eslint-disable-next-line no-new-func
+              new Function(
+                `return typeof ${
+                  parts[0]
+                } === 'undefined' ? undefined : ${parts.shift()}`
+              )()
+            : window
+
+          const value = parts.reduce(
             (value, method) =>
               value &&
               value instanceof Object &&
               Object.prototype.hasOwnProperty.call(value, method)
                 ? value[method]
                 : '__UNDEFINED__',
-              window
+            root || '__UNDEFINED__'
           )
 
           if (value !== '__UNDEFINED__') {