Can't Toggle Navbar in Bootstrap 4 in Angular

It looks like you might have been looking at this example from Bootstrap. I did, and had the same issue.

The problem is it is not an angular example so it won't work. To make it work you have to use the (click) event and a variable. So change your template to

<nav class="navbar navbar-expand-md navbar-dark fixed-top bg-dark">
  <a class="navbar-brand" href="#">Dashboard</a>
  <button class="navbar-toggler d-lg-none" type="button" (click)="isCollapsed = !isCollapsed" [attr.aria-expanded]="!isCollapsed" aria-controls="navbarsExampleDefault" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarsExampleDefault" [ngbCollapse]="isCollapsed">
    <ul class="navbar-nav mr-auto">
      <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="#">Settings</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Profile</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Help</a>
      </li>
    </ul>
    <form class="form-inline mt-2 mt-md-0">
      <input class="form-control mr-sm-2" type="text" placeholder="Search" aria-label="Search">
      <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>

If you want your menu to be collapsed by default you should set the variable to true in your class (in your .ts file for the component) public isCollapsed = true;

Here's a plunker

One more thing; If your nav is in a shared module you must remember to import NgbCollapseModule here as well.

That is, your shared.module.ts should be:

import { NgModule } from '@angular/core';
import { NgbCollapseModule } from '@ng-bootstrap/ng-bootstrap';
/*Plus all your other modules*/

@NgModule({
  imports: [NgbCollapseModule],
  declarations: [],
  exports: []
})
export class SharedModule {}

@Joseph, it looks like you haven't installed the dependencies for bootstrap (and bootstrap itself) for the navbar toggle to work.

If you open up terminal or the command line and navigate to the directory that contains your package.json file, run the following commands:

npm install --save jquery
npm install --save popper.js
npm install --save [email protected]

These commands will install the requisite dependencies for you project. They're fairly explicit in what they're doing, but if you need a refresh on what they're doing or how they work, I would suggest looking at the documentation for npm install located here.

After they're installed, you'll want to make sure you include them in your .angular-cli.json file, so you're angular app can use them.

This example provides both, toggling functionality for the hamburger icon (in other words the whole navbar if it's running in responsive mode) as well as toggling of dropdown menu items.

It uses ng-bootstrap but I would rather go with native Bootstrap navbar support instead of doing this "hacks"!?

Obviously others struggle with the same issue: https://github.com/twbs/bootstrap/issues/24227

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">ApplicationName</a>
  <button class="navbar-toggler" type="button" (click)="toggleNavbar = !toggleNavbar">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" [ngbCollapse]="!toggleNavbar">
    <ul class="navbar-nav">
      <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="#">Features</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Pricing</a>
      </li>
      <li ngbDropdown class="nav-item">
        <a class="nav-link" id="navbarDropdownMenuLink" ngbDropdownToggle aria-haspopup="true" aria-expanded="false">
          Dropdown link
        </a>
        <div ngbDropdownMenu aria-labelledby="navbarDropdownMenuLink">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <a class="dropdown-item" href="#">Something else here</a>
        </div>
      </li>
    </ul>
  </div>
</nav>