fix: warn about unknown function name (#237)

lib/__tests__/_getFunctionalInterface.test.ts

@@ -0,0 +1,20 @@
+import AlgoliaAnalytics from "../insights";
+import { getFunctionalInterface } from "../_getFunctionalInterface";
+
+describe("_getFunctionalInterface", () => {
+  let aa;
+
+  beforeEach(() => {
+    const analyticsInstance = new AlgoliaAnalytics({ requestFn: () => {} });
+    aa = getFunctionalInterface(analyticsInstance);
+  });
+
+  it("warn about unknown function name", () => {
+    console.warn = jest.fn();
+    aa("unknown-function");
+    expect(console.warn).toHaveBeenCalledTimes(1);
+    expect(console.warn).toHaveBeenCalledWith(
+      "The method `unknown-function` doesn't exist."
+    );
+  });
+});

lib/_getFunctionalInterface.ts

@@ -5,6 +5,8 @@ export function getFunctionalInterface(instance: AlgoliaAnalytics) {
   return (functionName: string, ...functionArguments: any[]) => {
     if (functionName && isFunction((instance as any)[functionName])) {
       instance[functionName](...functionArguments);
+    } else {
+      console.warn(`The method \`${functionName}\` doesn't exist.`);
     }
   };
 }