title: Bootstrap 4.2.1 hamburger not clickable
body: <p>I am using bootstrap 4.2.1 and my navbar collapses when the window shrinks, but the hamburger button does not show a menu when clicked. I had trouble making a plunker for it apologies. Why doesn't the dropdown menu show when I click the hamburger button? I feel like it might be a local problem, I've copied other people plunkrs and the bootstrap example and it doesn't work.</p>
  
  <pre><code>&lt;header id="header"&gt;
    &lt;nav class="navbar navbar-expand-md navbar-dark fixed-top bg-dark" role="navigation" &gt;
        &lt;button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation"&gt;
          &lt;span class="navbar-toggler-icon"&gt;&lt;/span&gt;
        &lt;/button&gt;
      &lt;div id="navbarSupportedContent" class="collapse navbar-collapse"&gt;
        &lt;div class="navbar-nav"&gt;
            &lt;a class=" nav-item nav-link" routerLinkActive="active" routerLink="/home"&gt;&lt;span class="sr-only"&gt;(current)&lt;/span&gt;{{home}}&lt;/a&gt;
            &lt;a class="nav-item nav-link" routerLinkActive="active" routerLink="/resume"&gt;{{resume}}&lt;/a&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/nav&gt;
  &lt;/header&gt;
  &lt;body class="main-container container-fluid"&gt;
      &lt;div id="view"&gt;
          &lt;router-outlet&gt;&lt;/router-outlet&gt;
      &lt;/div&gt;
  &lt;/body&gt;
  &lt;footer id="footer"&gt;
      &lt;div class="container-fluid navbar-expand-md navbar-dark bg-dark"&gt;
          &lt;span class="text-muted d-flex justify-content-center"&gt;{{copyright}}&lt;/span&gt;
      &lt;/div&gt;
  &lt;/footer&gt;
  </code></pre>
  
  <p>package.json</p>
  
  <pre><code>  {
    "name": "k",
    "version": "0.0.0",
    "scripts": {
      "ng": "ng",
      "start": "ng serve",
      "build": "ng build",
      "test": "ng test",
      "lint": "ng lint",
      "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
      "@angular/animations": "~7.1.4",
      "@angular/common": "~7.1.4",
      "@angular/compiler": "~7.1.4",
      "@angular/core": "~7.1.4",
      "@angular/forms": "~7.1.4",
      "@angular/http": "~7.1.4",
      "@angular/platform-browser": "~7.1.4",
      "@angular/platform-browser-dynamic": "~7.1.4",
      "@angular/router": "~7.1.4",
      "bootstrap": "^4.2.1",
      "core-js": "^2.5.4",
      "jquery": "^3.3.1",
      "popper.js": "^1.14.6",
      "rxjs": "~6.3.3",
      "tslib": "^1.9.0",
      "zone.js": "~0.8.26"
    },
    "devDependencies": {
      "@angular-devkit/build-angular": "~0.11.4",
      "@angular/cli": "~7.1.4",
      "@angular/compiler-cli": "~7.1.4",
      "@angular/language-service": "~7.1.4",
      "@types/jasmine": "~3.3.5",
      "@types/jasminewd2": "~2.0.3",
      "@types/node": "~10.12.18",
      "codelyzer": "~4.5.0",
      "jasmine-core": "~3.3.0",
      "jasmine-spec-reporter": "~4.2.1",
      "karma": "~3.1.4",
      "karma-chrome-launcher": "~2.2.0",
      "karma-coverage-istanbul-reporter": "~2.0.1",
      "karma-jasmine": "~2.0.1",
      "karma-jasmine-html-reporter": "^1.4.0",
      "protractor": "~5.4.0",
      "ts-node": "~7.0.0",
      "tslint": "~5.12.0",
      "typescript": "^3.1.6"
    }
  }
  </code></pre>