Bootstrap 4 scrollspy not working with Angular 4

I'm trying to implement scrollspy in Angular 4. I've imported jQuery and Bootstrap.js in .angular-cli.json file. Its not giving any error in the console. However active class is not getting applied to li element as expected.

https://v4-alpha.getbootstrap.com/components/scrollspy/

header.component.ts

ngOnInit() {
    $(document).ready(() => {
        $('body').scrollspy({target: "#myNavbar", offset: 50});   
    });
}

header.component.html

<div class="navbar-collapse" id="myNavbar">
  <ul class="nav navbar-nav">
    <li><a href="#PATIENT IDENTIFICATION">Section 1</a></li>
    <li><a href="#INITIATION">Section 2</a></li>
    <li><a href="#section3">Section 3</a></li>
    <li class="dropdown"><a class="dropdown-toggle" data-toggle="dropdown" href="#">Section 4 <span class="caret"></span></a>
      <ul class="dropdown-menu">
        <li><a href="#section41">Section 4-1</a></li>
        <li><a href="#section42">Section 4-2</a></li>
      </ul>
    </li>
  </ul>
</div>