diff --git a/ch00/test.js b/ch00/test.js
new file mode 100644
index 0000000..ef7d746
--- /dev/null
+++ b/ch00/test.js
@@ -0,0 +1,6 @@
+let uniqueInteger = (function () { // Define and invoke
+    let counter = 0; // Private state of function below 
+    return function() { return counter++; };
+}());
+console.log(uniqueInteger()) // => 0 
+console.log(uniqueInteger()) // => 1
\ No newline at end of file