title: Typescript callback with variable parameters undefined
body: <p>I having trouble to pass multiple parameters through a callback function.
  For some reason is one of the objects undefined. </p>
  
  <p>How do i define a callback functions with multiple parameters ? </p>
  
  <pre><code>  public save() {
      let oldStartDate = "2019-01-01";
  
      let newProject = new Project();
      newProject.oldStartDate = "2018-01-01";
  
      this.doSomeWork(newProject, this.workFinished_Callback.bind(this), oldStartDate);
    }
  
    public doSomeWork(project:Project, callback: (updatedProject: Project, ...param: any[]) =&gt; any = null, ...callbackArgs: any[]) {
      //Work work..
      console.log(project); //This exists..
  
      callback.call(project, ...callbackArgs);
    }
  
    public workFinished_Callback(project:Project, oldStartDate: string) {
      console.log(project); //This is undefined..
      console.log(oldStartDate); //Shows 2018-01-01
    }
  </code></pre>