Simplifying JavaScript

Tip 13

Update Key-Value Data Clearly with Maps

In this tip, you’ll learn how to use the Map object for key-value collections of frequently updated data.

In Tip 10, ​ Use Objects for Static Key-Value Lookups ​, you learned that you should only use objects deliberately and not as a default collection. Now you’re going to get a chance to look at an alternative: Map.

Map is a special kind of collection that can do certain things very easily. The Mozilla Developer Network has a nice list of circumstances where Map is a better option for a collection than a plain object.^[13] I encourage you to read the full list, but this tip examines two specific situations:

• Key-value pairs are frequently added or removed.
• A key isn’t a string.

In the next tip, you’ll ...