Use Map instead of Object

workflow/memoization.md

@@ -2,16 +2,16 @@
 
 Just calculate the value of something once, and reuse the value avoiding the cost of recalculate the same value.
 
-If you need to control of a set of tiny values, you can use an object:
+If you need to control of a set of tiny values, you can use an `Map`:
 
 ```js
-var cache = {}
+var cache = new Map()
+
 var cityOne = 'Murcia'
 var cityTwo = 'Madrid'
-var routeName = cityOne + '-' +  cityTwo
+var routeName = `${cityOne}${cityTwo}`
 
-if (!cache[routeName]) cache[routeName] = getDistance(cityOne, cityTwo)
-return cache[routeName]
+if (!cache.has(routeName)) cache.set(routeName, getDistance(cityOne, cityTwo))
 ```
 
-If you actually don't know how your cache could grow in memory, be careful. You need a little more sophisticated way as [lru-cache](https://www.npmjs.com/package/lru-cache) to control it.
+A little complex but better solution will be control the size of the `Map`, as LRU cache.