Singleton.html

<!DOCTYPE html>
<html>
  <head> </head>

  <body>
    <script>
      class Item {
        constructor(id, nome) {
          this.id = id;
          this.nome = nome;
        }
      }
      class Singleton {
        constructor() {
          if (!Singleton.instance) {
            this.id = "Single";
            this.data = [];
            Singleton.instance = this;
          }
          return Singleton.instance;
        }

        add(item) {
          this.data.push(item);
        }

        get(id) {
          return this.data.find(d => d.id === id);
        }
        findItem(nome) {
          return this.data.find(d => d.nome.includes(nome));
        }
      }

      const instance = new Singleton();
      const instance2 = new Singleton();
      Object.freeze(instance);
      var numItems = 1000;
      for (let i = 1; i <= numItems; i++) {
        item = new Item(i, makeid());
        instance.add(item);
      }
      console.log(instance.findItem("f1"));
      console.log(instance);
      console.log(instance2);

      function makeid() {
        let text = "";
        let possible =
          "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        for (let i = 0; i < 16; i++)
          text += possible.charAt(Math.floor(Math.random() * possible.length));
        return text;
      }
    </script>
  </body>
</html>