Bootstrap Dropdown button not opening on click - html

I am trying to build a navbar with buttons using bootstrap but the dropdowns aren't opening on click. I have included the bootstrap CDN link, bootstrap css link, ajax popper link and the jquery link in the code in the right places. I haven't added any external CSS to the navbar buttons. What can be the issue here?
Here is a snippet:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>Page Title</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<script defer src="https://use.fontawesome.com/releases/v5.0.6/js/all.js"></script>
<script src="main.js"></script>
</head>
<body>
<nav class="navbar navbar-expand-lg navbar fixed-top navbar-light bg-light">
<span class="navbar-toggler-icon"></span>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto ">
<li class="nav-item">
<div class="new-pickup"> <a class="nav-link" id="new-pickup" href="#"><i class="fa fa-plus"id="add-plus" aria-hidden="true"></i>
New Pickup </a></div>
<li class="nav-item dropdown">
<div class="sms-button">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
SMS
</a>
</div>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Delivered Status</a>
<a class="dropdown-item" href="#">Log details</a>
</div>
</li>
<li class="nav-item dropdown">
<div class="email-button">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Email
</a>
</div>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Deivered Status</a>
<a class="dropdown-item" href="#">Log Status</a>
</div>
</li>
<li class="nav-item">
<div class="call-button">
<a class="nav-link" href="#"><i class="fa fa-phone fa-flip-horizontal " aria-hidden="true"></i>
Call
</a></div>
</li>
</li>
</ul>
</div>
</nav>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
</body>
</html>
The main.js file has:
$(document).ready(function(){
$(".dropdown, .btn-group").hover(function(){
var dropdownMenu = $(this).children(".dropdown-menu");
if(dropdownMenu.is(":visible")){
dropdownMenu.parent().toggleClass("open");
}
});
});


This may be because you've added another div in there.
Try rearranging your code so that the element with the class .dropdown-toggle is the next item. Rather than div.sms-button


Try below Code:
Option : 1
<li class="nav-item dropdown">
<div class="sms-button" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
<a class="nav-link dropdown-toggle" href="#" > SMS </a>
</div>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Delivered Status</a>
<a class="dropdown-item" href="#">Log details</a>
</div>
</li>
Option : 2
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> Email </a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Deivered Status</a>
<a class="dropdown-item" href="#">Log Status</a>
</div>
</li>


Add data-toggle="collapse" data-target=".navbar-collapse" to your clickable icon
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<script defer src="https://use.fontawesome.com/releases/v5.0.6/js/all.js"></script>
<script src="main.js"></script>
<nav class="navbar navbar-expand-lg navbar fixed-top navbar-light bg-light">
<!--code changes here-->
<span class="navbar-toggler-icon" data-toggle="collapse" data-target=".navbar-collapse"></span>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto ">
<li class="nav-item">
<div class="new-pickup"> <a class="nav-link" id="new-pickup" href="#"><i class="fa fa-plus"id="add-plus" aria-hidden="true"></i>
New Pickup </a></div>
<li class="nav-item dropdown">
<div class="sms-button">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
SMS
</a>
</div>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Delivered Status</a>
<a class="dropdown-item" href="#">Log details</a>
</div>
</li>
<li class="nav-item dropdown">
<div class="email-button">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Email
</a>
</div>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Deivered Status</a>
<a class="dropdown-item" href="#">Log Status</a>
</div>
</li>
<li class="nav-item">
<div class="call-button">
<a class="nav-link" href="#"><i class="fa fa-phone fa-flip-horizontal " aria-hidden="true"></i>
Call
</a></div>
</li>
</li>
</ul>
</div>
</nav>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

Related

Dropdown menu go outside of page

I'm trying to add a dropdown menu on top right.
This is what I have :
The menu which is open of the dropdown is outside the page.
This is my code:
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mx-auto">
<li class="nav-item">
<a class="nav-link" href="#">something</a>
</li>
</ul>
<ul class="navbar-nav ml-auto">
<li class="nav-item">
<a class="nav-link" href="#">Link</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
</ul>
</div>
</nav>
(You should open in full page)
How can I make the dropdown menu don't go outside? Like limit it to the right side.

You can add dropdown-menu-rightclass to your dropdown
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mx-auto">
<li class="nav-item">
<a class="nav-link" href="#">something</a>
</li>
</ul>
<ul class="navbar-nav ml-auto">
<li class="nav-item">
<a class="nav-link" href="#">Link</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu dropdown-menu-right" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
</ul>
</div>
</nav>

Bootstrap navbar toggle is not working (expanding)

I am struggling with my navbar that was made out of HTML CSS and Bootstrap. I had followed some tutorials on youtube but I can seem to expand the toggle button when the screen size is reduced to the smallest. Since I'm starting a new project, I applied all of this with HTML CSS, and Bootstrap and opened the HTML file in my local directory. Please help me! I have been stuck for hours.
Below are the codes that I did:
<head>
<meta charset="UTF-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<meta http-equiv="X-UA-Compatible" content="ie=edge"/>
<script src="https://code.jquery.com/jquery-3.5.1.js"></script>
<link rel="stylesheet" href="bootstrap.min.css"/>
<link rel="stylesheet" href="title.css" />
<title>Document</title>
</head>
<body>
<nav class="navbar navbar-expand-md navbar-light bg-light sticky-top">
<button class="navbar-toggler" data-toggle="collapse" data-target="#collapse_target">
<span class="navbar-toggler-icon></span>
</button>
<div class="collapse navbar-collapse" id="collapse_target">
<a class="navbar-brand>Logo</a>
<ul class="navbar-nav">
<li class="nav-item">
<a class="nav-link href="#">Link 1</a>
</li>
<li class="nav-item">
<a class="nav-link href="#">Link 2</a>
</li>
<li class="nav-item">
<a class="nav-link href="#">Link 3</a>
</li>
</ul>
</div>
</nav>
</body>
My results are as below:
I will get the toggler icon as above but I will not be able to click it and get 'Home', 'Categories', 'About', and 'Contact'. I don't know where I did wrong.
Thank you for your time.

You missed JS, their CDN is available in getbootstrap.com
I add two responsive navbar in the following. These codes are used from getbootstrap.com
<!doctype html>
<html lang="en">
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<!-- Bootstrap CSS -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap#4.5.3/dist/css/bootstrap.min.css" integrity="sha384-TX8t27EcRE3e/ihU7zmQxVncDAy5uIKz4rEkgIXeMed4M0jlfIDPvg6uqKI2xXr2" crossorigin="anonymous">
<title>Document</title>
</head>
<body>
<nav class="navbar navbar-expand-sm navbar-dark bg-dark">
<a class="navbar-brand" href="#">Expand at sm</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarsExample03" aria-controls="navbarsExample03" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarsExample03">
<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="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="dropdown03" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dropdown</a>
<div class="dropdown-menu" aria-labelledby="dropdown03">
<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>
<form class="form-inline my-2 my-md-0">
<input class="form-control" type="text" placeholder="Search">
</form>
</div>
</nav>
<hr class"m-5">
<nav class="navbar navbar-expand-xl navbar-dark bg-dark">
<a class="navbar-brand" href="#">Expand at xl</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarsExample06" aria-controls="navbarsExample06" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarsExample06">
<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="#">Link</a>
</li>
<li class="nav-item">
<a class="nav-link disabled" href="#" tabindex="-1" aria-disabled="true">Disabled</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="dropdown06" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dropdown</a>
<div class="dropdown-menu" aria-labelledby="dropdown06">
<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>
<form class="form-inline my-2 my-md-0">
<input class="form-control" type="text" placeholder="Search">
</form>
</div>
</nav>
<!-- Optional JavaScript; choose one of the two! -->
<!-- Option 1: jQuery and Bootstrap Bundle (includes Popper) -->
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap#4.5.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ho+j7jyWK8fNQe+A12Hb8AhRq26LrZ/JpcUGGOn+Y7RsweNrtN/tE3MoK7ZeZDyx" crossorigin="anonymous"></script>
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js#1.16.1/dist/umd/popper.min.js" integrity="sha384-9/reFTGAW83EW2RDu2S0VKaIzap3H66lZH81PoYlFhbGU+6BZp6G7niu735Sk7lN" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap#4.5.3/dist/js/bootstrap.min.js" integrity="sha384-w1Q4orYjBQndcko6MimVbzY0tgp4pWB4lZ7lr30WKz0vr/aWKhXdBNmNb5D92v7s" crossorigin="anonymous"></script>
</body>
</html>

Bootstrap requires JavaScript to function properly. You should add the scripts Bootstrap requires. Source: https://getbootstrap.com/docs/4.5/getting-started/introduction/#js
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap#4.5.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ho+j7jyWK8fNQe+A12Hb8AhRq26LrZ/JpcUGGOn+Y7RsweNrtN/tE3MoK7ZeZDyx" crossorigin="anonymous"></script>

It looks like you are missing "type: button" in your button tag as seen below:
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapse_target">

Your problem in Javascript. Please add Boostrap JS into your code.
You can run this code to your page.
Example:
<html>
<head>
<meta charset="UTF-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<meta http-equiv="X-UA-Compatible" content="ie=edge"/>
<script src="https://code.jquery.com/jquery-3.5.1.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js"></script>
<title>Document</title>
</head>
<body>
<nav class="navbar navbar-expand-lg navbar-light bg-light container">
<a class="navbar-brand" href="#">Boostrap</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto">
<li class="nav-item active">
<a class="nav-link" href="#">Now<span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Can</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Use</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link disabled" href="#">Donate Me</a>
</li>
</ul>
<form class="form-inline my-2 my-lg-0">
<input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
<button class="btn btn-outline-success my-2 my-sm-0" type="submit">Searching</button>
</form>
</div>
</nav>
</body>
</html>

How do I fix this Navbar glitch from bootstrap. It keeps sliding back up when i press the toggle button

<!DOCTYPE html>
<html>
<head>
<title>Home Page</title>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<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 class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown link
</a>
<div class="dropdown-menu" 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>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<!-- jQuery library -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<!-- Latest compiled JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js"></script>
</head>
<body>
<h1 class = "header" >Hello World! </h1>
</body>
</html>
I copied and pasted this straight from the bootstrap website. I am new to html and bootstrap. Pls help. I think if u copy paste this code to a html file, and then open it in a small browser window and press the toggle button, u will see what i mean.

This is because your bootstrap's js has 3.4.1 and css has 4.0.0. Please add same versions.
<!DOCTYPE html>
<html>
<head>
<title>Home Page</title>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<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 class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown link
</a>
<div class="dropdown-menu" 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>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<!-- jQuery library -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<!-- Latest compiled JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
</head>
<body>
<h1 class = "header" >Hello World! </h1>
</body>
</html>

A few things:
You're missing some necessities. Move the <nav> into the <body> (not in the <head>). You then need these added right before the </body>:
<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js#1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>
Here is a working Codepen to show you.

Bootstrap dropdown on navbar pushing content down

I'm using a dropdown option on the top navbar on bootstrap and it has one quirk, it pushes the content on the left of the navbar down as the navbar appears like so.
before click
after click
This is the html used
<!DOCTYPE html>
<html>
<head>
<title>Notifications</title>
<meta charset="utf-8"/>
<link rel="stylesheet" type="text/css" href="css/bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="css/notification.css">
<script type="text/javascript" src="js/jquery-3.3.1.slim.min.js"></script>
<script type="text/javascript" src="js/popper.min.js"></script>
<script type="text/javascript" src="js/bootstrap.min.js"></script>
</head>
<body>
<!-- Image and text -->
<nav class="navbar navbar-light">
<a class="navbar-brand" href="#">
<img src="img/bootstrap-solid.svg" width="30" height="30" class="d-inline-block align-top" alt="">
Bootstrap
</a>
<ul class="navbar-nav">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Notifications <span class="badge badge-secondary">0</span>
</a>
<div class="dropdown-menu" 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>
</nav>
</body>
</html>

The default definition for a nav in bootstrap is to push down content.
You can setposition: absolute; on ul
ul{
position: absolute;
right: 50px;
top: 14px;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
<!-- Image and text -->
<nav class="navbar navbar-light">
<a class="navbar-brand" href="#">
<img src="img/bootstrap-solid.svg" width="30" height="30" class="d-inline-block align-top" alt="">
Bootstrap
</a>
<div>
<ul class="navbar-nav">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Notifications <span class="badge badge-secondary">0</span>
</a>
<div class="dropdown-menu" 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>

.dropdown-menu{
position:absolute;
}
Making the dropdown as position absolute, will give you the desired output.

Try putting the contents within a single 'div' element as in the code segment below:
<body>
<!-- Image and text -->
<nav class="navbar navbar-light">
<div class="container">
<a class="navbar-brand" href="#">
<img src="img/bootstrap-solid.svg" width="30" height="30" class="d-inline-block align-top" alt="">Bootstrap
</a>
<ul class="navbar-nav">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Notifications <span class="badge badge-secondary">0</span>
</a>
<div class="dropdown-menu" 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>
</body>

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" integrity="sha384-WskhaSGFgHYWDcbwN70/dfYBj47jz9qbsMId/iRN3ewGhXQFZCSftd1LZCfmhktB" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js" integrity="sha384-smHYKdLADwkXOn1EmN1qk/HfnUcbVRZyYmZ4qpPea6sjB/pTJ0euyQp0Mk8ck+5T" crossorigin="anonymous"></script>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Navbar</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarNavDropdown">
<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 class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown link
</a>
<div class="dropdown-menu" 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>

For icons in the top right of a webpage...
Make sure your CSS file comes after the bootstrap lib CSS file.
Insert the below code into your CSS file.
Add id="dropdownMenu" to your
html tag. This should prevent the popup from going off the page while also preventing the navbar from ballooning out.
#dropdownMenu {
position: absolute;
left: auto;
right: 0;
}

This happens because bootstrap have css like :
.navbar-nav .dropdown-menu{
position: static;
}
To avoid the problem of pushing the content down on dropdown. Just sipmly add css :
.navbar-nav .dropdown-menu{
position: absolute;
}
in case your menus are on the right side and content gets overflow or not correctly visible then just simply add to
<div class="dropdown-menu dropdown-menu-right" aria-labelledby="navbarDropdown">
for getting menu dropdown to align-right

HTML page width change when i open dropdown

I'm having trouble with my navbar. when i open my dropdown, my page width is change when it closed, my page back in normal.
<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet" />
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js" integrity="sha384-vFJXuSJphROIrBnz7yo7oB41mKfc8JzQZiCq4NCceLEaO4IHwicKwpJf9c9IpFgh" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js" integrity="sha384-alpBpkh1PFOepccYVYDB4do5UnbKysX5WZXm3XxPqe5iKTfUKjNkCk9SaVuEZflJ" crossorigin="anonymous"></script>
<nav class="navbar navbar-expand-lg navbar-light sticky-top">
<div class="navbar-collapse" id="navbarTogglerDemo01">
<ul id="forside" class="navbar-nav mr-auto">
<a id="sidebarCollapse" class="navbar-brand" href="#"><i class="fa fa-list"></i></a>
</ul>
<ul class="navbar-nav pull-right">
<li class="nav-item">
<a class="nav-link" href="#"><span class="fa fa-envelope"></span></a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="#"><span class="fa fa-cogs"></span></a>
</li>
</ul>
</div>
</nav>
And here is a screenshot when my dropdown is closed
and here is the screenshot when i open my dropdown
as you can see there is a scroll below. i need to scroll it first to see my full dropdown item. So, how can i fix it ? i don't want to scroll to see my dropdown item. sorry for my english

Give this css to align popup right and scroll is remove. Check in full page.
.navbar-expand-lg .navbar-nav .dropdown-menu {
left: auto;
right: 0;
}
.navbar-expand-lg .navbar-nav .dropdown-menu {
left: auto;
right: 0;
}
<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet" />
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js" integrity="sha384-vFJXuSJphROIrBnz7yo7oB41mKfc8JzQZiCq4NCceLEaO4IHwicKwpJf9c9IpFgh" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js" integrity="sha384-alpBpkh1PFOepccYVYDB4do5UnbKysX5WZXm3XxPqe5iKTfUKjNkCk9SaVuEZflJ" crossorigin="anonymous"></script>
<nav class="navbar navbar-expand-lg navbar-light sticky-top">
<div class="navbar-collapse" id="navbarTogglerDemo01">
<ul id="forside" class="navbar-nav mr-auto">
<a id="sidebarCollapse" class="navbar-brand" href="#"><i class="fa fa-list"></i></a>
</ul>
<ul class="navbar-nav pull-right">
<li class="nav-item">
<a class="nav-link" href="#"><span class="fa fa-envelope"></span></a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Action</a>
<a class="dropdown-item" href="#">Another action</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="#">Something else here</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="#"><span class="fa fa-cogs"></span></a>
</li>
</ul>
</div>
</nav>