angular collapse code example

Example 1: ngfor

<li *ngFor="let item of items; index as i; trackBy: trackByFn">...</li>

Example 2: collapse in angular 4

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler btn btn-outline-primary" type="button" data-toggle="collapse" data-target="#navbarTogglerDemo02"  aria-expanded="false" aria-label="Toggle navigation" (click)="isCollapsed = !isCollapsed" [attr.aria-expanded]="!isCollapsed" aria-controls="navbarTogglerDemo02">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarTogglerDemo02" [ngbCollapse]="isCollapsed">
    <ul class="navbar-nav mr-auto mt-2 mt-lg-0">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Link</a>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="search" placeholder="Search">
      <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>