Creating a WeakSet from existing data

We just saw how to create a Set from existing data. The related class WeakSet can be created in a similar way, but has restrictions on membership. In this recipe, we'll take a look at how to create a WeakSet from existing data and some restrictions on membership.

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 12-04-create-weak-set-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 a main function with an array of rocket instances. Create a new WeakSet from the array. Try to add a string to WeakSet:

// main.js 
export function main() { ...