Creating a Map from the existing data

We just saw how to add values individually to maps. This can be tedious, however. For example, if we are working with a dataset that might be very large or unknown ahead of time, it would be nice to initialize a map with a function call rather than hundreds or thousands.

In this recipe, we'll take a look at how to create a new Map with the preexisting data.

Getting ready

This recipe assumes that you already have a workspace that allows you to create and run ES modules in your browser. If you don't, refer to the first two chapters.

How to do it...

1. Open your command-line application and navigate to your workspace.
2. Create a new folder named 11-05-create-map-from-data.
3. Create a main.js file that defines a new class named Rocket that takes a constructor argument name and assigns it to an instance property:

// main.js 
class Rocket { 
  constructor(name) { 
    this.name = name; 
  } 
   } 

4. Create an enum of various launch sites:

// main.js 
const LaunchSite = { 
 ...