Navbar Toggle Icon not displaying

[connorsleight]

I cloned the repo, ran the project ng serve and the Navbar Toggle Icon doesnt appear to display. The code on the page is as follows:

<nav class="navbar navbar-toggleable-md bg-primary navbar-inverse">
    <button class="navbar-toggler navbar-toggler-right" type="button"
            data-toggle="collapse" data-target="#myNavBar">
        <span class="navbar-toggler-icon"></span>
    </button>
    <a href="/" class="navbar-brand">Bootstrap Webinar</a>
    <div class="navbar-collapse collapse" id="myNavBar">
        <ul class="navbar-nav">
            <li class="nav-item">
                <a routerLink="/bootstrap" routerLinkActive="active" class="nav-link" href="#">Bootstrap</a>
            </li>
            <li class="nav-item">
                <a routerLink="/widgets" routerLinkActive="active" class="nav-link">Widgets</a>
            </li>
            <li class="nav-item">
                <a routerLink="/about" routerLinkActive="active" class="nav-link" href="#">About</a>
            </li>
        </ul>
    </div>
</nav>