[Draft] Memoize limit

packages/function-memoize/index.js

@@ -23,7 +23,40 @@ module.exports = memoize;
  sum(10, 20) -- Cache hit!
 */
 
-function memoize(callback, resolver) {
+function Order() {
+ this.keys = [];
+ this.cache = {};
+}
+
+Order.prototype = {
+ 'has': function(key) {
+ return this.cache.hasOwnProperty(key);
+ },
+
+ 'get': function(key) {
+ return this.cache[key];
+ },
+
+ 'set': function(key, value) {
+ if (!this.has(key)) {
+ this.keys.push(key);
+ }
+
+ this.cache[key] = value;
+ },
+
+ 'delete': function(key) {
+ var index = this.keys.indexOf(key);
+ this.keys.splice(index, 1);
+ delete this.cache[key];
+ },
+
+ 'keys': function() {
+ return this.keys;
+ },
+};
+
+function memoize(callback, resolver, options) {
  if (typeof callback !== 'function') {
  throw new Error('`callback` should be a function');
  }
@@ -32,17 +65,26 @@ function memoize(callback, resolver) {
  throw new Error('`resolver` should be a function');
  }
 
- var cache = {};
+ if (options !== undefined && typeof options !== 'object') {
+ throw new Error('`options` should be an object');
+ }
+
+ var cache = 'Map' in (typeof window === 'undefined' ? global : window) ? new Map() : new Order();
 
  var memoized = function() {
  var args = Array.prototype.slice.call(arguments); // to simplify JSON.stringify
  var key = resolver ? resolver.apply(this, args) : JSON.stringify(args);
 
- if (!(key in cache)) {
- cache[key] = callback.apply(this, args);
+ if (!cache.has(key)) {
+ cache.set(key, callback.apply(this, args));
+ }
+
+ if (typeof options.max === 'number' && cache.size > options.max) {
+ var firstKey = cache.keys()[0];
+ cache.delete(firstKey);
  }
 
- return cache[key];
+ return cache.get(key);
  };
 
  memoized.cache = cache;