These look and work similarly to how they do in Java: if a member has the static keyword modifier, it exists on the class instead of object instances. You could add a static member to the Song class as shown in Listing 3. The class fields proposal also introduces static members. The hash symbol also works as a prefix on methods and accessors. The effect on visibility is exactly the same as it is with private instance fields. So, you could add a private setter and a public getter to the Song.artist field, as shown in Listing 2. Overall, this is a nice addition, making for cleaner code. Most browsers have supported public and private instance fields for a while and it’s nice to see them officially incorporated. Note, also, that even song1.hasOwnProperty('artist') will return false. Additionally, we cannot create private fields on the class later using assignment. Next, we define an instance of the Song class, setting both fields via the constructor. We then output the fields to the console. The point is that song1.artist is not visible to the outside world, and outputs undefined. In Listing 1, we define a class, Song, using the class keyword. This class has two members, title and artist. The artist member is prefixed with a hash (#) symbol, so it is private. We allow for setting these fields in the constructor. Notice that the constructor must access this.#artist with the hash prefix again otherwise, it would overwrite the field with a public member. Let song1 = new Song('Only a Song', 'Van Morrison') Previously, the standard approach when declaring a member field inside the class keyword was to introduce it in the constructor. The newest ECMAScript specification lets us define the member field inline as part of the class body. As shown in Listing 1, we can use a hashtag to denote a private field.

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