chapter 02: add a inmemory calculator to continuing trying state-based testing

Author: devcorpio

chapter_02-a-first-unit-test/MemCalculator/memCalculator.js

@@ -0,0 +1,28 @@
+function memCalculator() {
+    /**
+     * @type {number}
+     */
+    let sum = 0;
+
+    /**
+     * @param {number} number
+     */
+    function add(number) {
+        sum += number;
+    }
+
+    /**
+     * @return {number}
+     */
+    function result() {
+        /**
+         * @type {number};
+         */
+        const temp = sum;
+        sum = 0;
+
+        return temp;
+    }
+}
+
+module.exports = memCalculator;