Add working implementation and tests

index.js

@@ -1,3 +1,13 @@
-const kekos = () => console.log("Kekos!");
+// https://keycode.info/
+// https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/code
 
-export default kekos;
+const kekos = ({
+  keyCodesPermitted = ["Enter", "Space"],
+  callback = () => {},
+}) => (event) => {
+  try {
+    if (keyCodesPermitted.includes(event.code)) callback(event);
+  } catch (_) {}
+};
+
+module.exports = kekos;

index.test.js

@@ -0,0 +1,32 @@
+const kekos = require("./");
+
+describe("Kekos", () => {
+  test("will not invoke the callback on configuration", () => {
+    const callback = jest.fn();
+    kekos({ callback });
+
+    expect(callback).not.toHaveBeenCalled();
+  });
+
+  test("will invoke the callback when permitted key code provided", () => {
+    const callback = jest.fn();
+    const event = { code: "Enter" };
+    const onKeyDown = kekos({ callback });
+
+    expect(callback).not.toHaveBeenCalled();
+
+    onKeyDown(event);
+
+    expect(callback).toHaveBeenCalledWith(event);
+  });
+
+  test("will not invoke the callback when unpermitted key code provided", () => {
+    const callback = jest.fn();
+    const event = { code: "ControlLeft" };
+    const onKeyDown = kekos({ callback });
+
+    onKeyDown(event);
+
+    expect(callback).not.toHaveBeenCalled();
+  });
+});