Solution

src/makeCalculator.js

@@ -4,7 +4,39 @@
  * @return {object}
  */
 function makeCalculator() {
-  // write code here
+  const calc = {
+    result: 0,
+
+    add(num) {
+      return calc.result + num;
+    },
+
+    subtract(num) {
+      return calc.result - num;
+    },
+
+    multiply(num) {
+      return calc.result * num;
+    },
+
+    divide(num) {
+      return calc.result / num;
+    },
+
+    reset() {
+      this.result = 0;
+
+      return this;
+    },
+
+    operate(callback, number) {
+      this.result = callback(number);
+
+      return this;
+    },
+  };
+
+  return calc;
 }
 
 module.exports = makeCalculator;