Classes, the modern parts in JavaScript

Field declarations, private members, static blocks and accessors.

class Session {
  #runs = [];
  static created = 0;

  static {
    Session.created = 0;
  }

  constructor(lang) {
    this.lang = lang;
    Session.created += 1;
  }

  record(tpm) {
    this.#runs.push(tpm);
    return this;
  }

  get best() {
    return this.#runs.length ? Math.max(...this.#runs) : 0;
  }

  static from(lang, ...runs) {
    const session = new Session(lang);
    runs.forEach((tpm) => session.record(tpm));
    return session;
  }
}

const session = Session.from("go", 98, 104);
console.log(session.best, Session.created, Object.keys(session));

How it works

1. A #name field is genuinely private: no reflection reaches it.
2. Class fields replace assigning in the constructor.
3. static members and blocks belong to the class itself.

Keywords and builtins used here

• Math
• Object
• class
• const
• constructor
• from
• return
• static
• this

The run, in numbers

Lines

31

Characters to type

508

Tokens

156

Three-star pace

95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 99 seconds.

Type this snippet

Step 2 of 3 in Classes, step 36 of 43 in Language basics.

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