Solution

src/makeCalculator.js

@@ -4,7 +4,43 @@
  * @return {object}
  */
 function makeCalculator() {
-  // write code here
-}
+  let result = 0;
+
+  const add = (a, b) => a + b;
+  const subtract = (a, b) => a - b;
+  const multiply = (a, b) => a * b;
+  const divide = (a, b) => a / b;
+
+  const operate = function (callback, num) {
+    if (callback === add) {
+      result += num;
+    } else if (callback === subtract) {
+      result -= num;
+    } else if (callback === multiply) {
+      result *= num;
+    } else if (callback === divide) {
+      result /= num;
+    }
+
+    return this;
+  };
 
+  const reset = function () {
+    result = 0;
+
+    return this;
+  };
+
+  return {
+    get result() {
+      return result;
+    },
+    add,
+    subtract,
+    multiply,
+    divide,
+    operate,
+    reset,
+  };
+}
 module.exports = makeCalculator;