1 files changed, 10 insertions, 21 deletions
diff --git a/lib/memoize.js b/lib/memoize.js
index ea0da43..d800106 100644
--- a/lib/memoize.js
+++ b/lib/memoize.js
@@ -1,13 +1,7 @@
-import identity from './internal/identity';
-import slice from './internal/slice';
 import setImmediate from './internal/setImmediate';
 import initialParams from './internal/initialParams';
 import wrapAsync from './internal/wrapAsync';
 
-function has(obj, key) {
-    return key in obj;
-}
-
 /**
  * Caches the results of an async function. When creating a hash to store
  * function results against, the callback is omitted from the hash and an
@@ -48,34 +42,29 @@ function has(obj, key) {
  *     // callback
  * });
  */
-export default function memoize(fn, hasher) {
+export default function memoize(fn, hasher = v => v) {
     var memo = Object.create(null);
     var queues = Object.create(null);
-    hasher = hasher || identity;
     var _fn = wrapAsync(fn);
-    var memoized = initialParams(function memoized(args, callback) {
-        var key = hasher.apply(null, args);
-        if (has(memo, key)) {
-            setImmediate(function() {
-                callback.apply(null, memo[key]);
-            });
-        } else if (has(queues, key)) {
+    var memoized = initialParams((args, callback) => {
+        var key = hasher(...args);
+        if (key in memo) {
+            setImmediate(() => callback(null, ...memo[key]));
+        } else if (key in queues) {
             queues[key].push(callback);
         } else {
             queues[key] = [callback];
-            _fn.apply(null, args.concat(function(/*args*/) {
-                var args = slice(arguments);
-                var err = args[0];
+            _fn(...args, (err, ...resultArgs) => {
                 // #1465 don't memoize if an error occurred
                 if (!err) {
-                    memo[key] = args;
+                    memo[key] = resultArgs;
                 }
                 var q = queues[key];
                 delete queues[key];
                 for (var i = 0, l = q.length; i < l; i++) {
-                    q[i].apply(null, args);
+                    q[i](err, ...resultArgs);
                 }
-            }));
+            });
         }
     });
     memoized.memo = memo;