singleton-registry.ts

class Registry {
  private static instance: Registry

  private constructor() {}

  protected list = []

  private static getInstance() {
    if (!Registry.instance) {
      Registry.instance = new Registry()
    }
    return Registry.instance
  }

  public static getList(): Array<string> {
    return Registry.getInstance().list
  }
}

let a = Registry.getList()
let b = Registry.getList()

console.log(a === b)

a.push('foo')

console.log(a, b)