Map summary

You've made it through maps! Here are some final thoughts.

Takeaways

• A Map is a highly flexible data structure that is used to store relationships, based around the idea of key value pairs.
• Maps are useful for storing information about something. For example, a hospital information card might best be implemented as a map.

Objects vs Maps

You may have noticed that the structure of Map is similar to a JavaScript object.

The Map type was only recently introduced in ECMA 6. Until then, in JavaScript, an Object was used in its place. There are a couple of notable differences between Objects and Maps.

• An Object has a prototype, which means that there are default keys in an object that could conflict with your keys.
• The keys of an Object are required to be Strings and Symbols, whereas they can be of any type in a Map, including objects, functions, or primitives.
• Getting the size of an Object often involved a lot of trickery.
• The Map has size built in as a property.

When to use a Map over an Object

So when should you use a Map over an Object?

If you answer yes to any of the questions below, use a Map.

• Are keys usually unknown until run time?
• Do you need to look up keys dynamically?
• Do all values have the same type?
• Do you need keys that aren't strings?
• Are key-value pairs often added or removed?
• Do you have a fluctuating amount of key-value pairs?
• Are the key-value pairs iterated?

• Additional information on maps can be found here.