Completed closure.js

williamantony · web-flow · commit d024b5ffbe03 · 2017-11-08T11:50:11.000-06:00
diff --git a/src/closure.js b/src/closure.js
@@ -4,18 +4,42 @@ const counter = () => {
   // Return a function that when invoked increments and returns a counter variable.
   // Example: const newCounter = counter();
   // newCounter(); // 1
-  // newCounter(); // 2
+  // console.log(...arg);
+  let count = 0;
+  return () => {
+    count++;
+    return count;
+  };
 };
 
 const counterFactory = () => {
   // Return an object that has two methods called `increment` and `decrement`.
   // `increment` should increment a counter variable in closure scope and return it.
   // `decrement` should decrement the counter variable and return it.
+  let count = 0;
+  return {
+    increment: () => {
+      count++;
+      return count;
+    },
+    decrement: () => {
+      count--;
+      return count;
+    },
+  };
 };
 
 const limitFunctionCallCount = (cb, n) => {
   // Should return a function that invokes `cb`.
   // The returned function should only allow `cb` to be invoked `n` times.
+  let count = 0;
+  return (...args) => {
+    if (count === n) {
+      return null;
+    }
+    count++;
+    return cb(...args);
+  };
 };
 
 /* STRETCH PROBLEM */
@@ -27,6 +51,14 @@ const cacheFunction = (cb) => {
   // If the returned function is invoked with arguments that it has already seen
   // then it should return the cached result and not invoke `cb` again.
   // `cb` should only ever be invoked once for a given set of arguments.
+  const cache = {};
+  return (arg) => {
+    if (arg in cache) {
+      return cache[arg];
+    }
+    cache[arg] = cb;
+    return cb(arg);
+  };
 };
 
 /* eslint-enable no-unused-vars */
