TypeScriptでインスタンスを共有する

instanceSharing.ts

class Test1{
  varStr: string;
  constructor(){
    this.varStr = "ABC";
  }
}

class Test2{
  private t1: Test1;
  
  constructor(t1: Test1){
    this.t1 = t1;
  }
  

  setVal(str: string){
    this.t1.varStr = str;
  }

  getVal(): string{
    return this.t1.varStr;
  }
}

class Test3{
  private t1: Test1;

  constructor(t1: Test1){
    this.t1 = t1;
  }

  getVal(): string{
    return this.t1.varStr;
  }
}

var t1 = new Test1();
var t2 = new Test2(t1);
var t3 = new Test3(t1);

console.log("FIRST - " + t1.varStr);
t2.setVal("XXX");

console.log("SECOND(t1) - " + t1.varStr);
console.log("SECOND(t2) - " + t2.getVal());
console.log("SECOND(t3) - " + t3.getVal());