fixed chuanxshi#6, now use hasOwnProperty for memoization pattern

chuanxshi · chuanxshi · commit 8a465a420454 · 2012-01-14T08:36:30.000+08:00
diff --git a/function-patterns/memoization.html b/function-patterns/memoization.html
@@ -6,6 +6,8 @@
 </head>
 <body>
 <script>
+  // antipattern
+  // reason see: https://github.com/shichuan/javascript-patterns/issues/6
   var myFunc = function (param) {
     if (!myFunc.cache[param]) {
       var result = {};
@@ -18,6 +20,28 @@
   // cache storage
   myFunc.cache = {};
   
+  
+  // preferred
+  
+  /*
+  only one argument using param
+  */
+  var myFunc = function (param) {
+    if (!myFunc.cache.hasOwnProperty(param)) {
+      var result = {};
+      // ... expsensive operation ...
+      myFunc.cache[param] = result;
+    }
+    return myFunc.cache[param];
+  };
+  
+  // cache storage
+  myFunc.cache = {};
+  
+  
+  /*
+  multiple arguments using JSON stringify
+  */
   var myFunc = function () {
     var cachekey = JSON.stringify(Array.prototype.slice.call(arguments)),
                    result;
@@ -32,6 +56,10 @@
   // cache storage
   myFunc.cache = {};
   
+  
+  /*
+  multiple arguments using arguments.callee
+  */
   var myFunc = function (param) {
     var f = arguments.callee,
         result;
