My bootstrap4 Navbar is not looking correctly - javascript

I'm using bootstrap version 4 and added in a Navbar but it came out looking like this and I am not sure why. I pasted the needed links and double checked however I still can't find the problem. I'm also new to using bootstrap so I would be grateful if anyone can help me.
A screenshot of how it is looking
Here's my code:
This is _document.js
import Document , {Html, Head, Main, NextScript} from 'next/document'
class MyDocument extends Document
{
render()
{
return (
<Html lang="en">
<head>
<meta name="Online shop" content="Online shop web app" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap#4.0.0/dist/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous"></link>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" ></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js#1.12.9/dist/umd/popper.min.js" ></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap#4.0.0/dist/js/bootstrap.min.js" ></script>
</head>
<body>
<Main />
<NextScript />
</body>
</Html>
)
}
}
export default MyDocument;
This is Navbar.js
import React from 'react'
import Link from 'next/link'
const Navbar = () => {
return (<div>
<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>
</div>)
}
export default Navbar;
I can't find where I went wrong.

Related

bootstrap 5 how to close the whole menu when click on the link or click outside on the page

I'm using BootStrap 5 to build my page
I have a NavBar Menu with links
<head>
<link href="https://cdn.jsdelivr.net/npm/bootstrap#5.0.0/dist/css/bootstrap.min.css" rel="stylesheet" >
<script src="https://cdn.jsdelivr.net/npm/#popperjs/core#2.9.2/dist/umd/popper.min.js" ></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap#5.0.1/dist/js/bootstrap.min.js" integrity="sha384-Atwg2Pkwv9vp0ygtn1JAojH0nYbwNJLPhwyoVbhoPwBhjQPR5VtM2+xf0Uwh9KtT" crossorigin="anonymous"></script>
</head>
<nav class="navbar navbar-expand-lg navbar-light bg-transparent pt-0 pb-0">
<div class="container">
<a class="navbar-brand pt-0 pb-0 me-0" href="#home">Salimi<span>Me</span></a>
<button class="navbar-toggler border-0" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav"
aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse justify-content-between" id="navbarNav">
<ul class="navbar-nav">
<li class="nav-item position-relative">
<a class="nav-link active" aria-current="page" href="#home">Home</a>
</li>
<li class="nav-item position-relative">
<a class="nav-link" href="#about">About</a>
</li>
<li class="nav-item position-relative">
<a class="nav-link" href="#skills">Skills</a>
</li>
<li class="nav-item position-relative">
<a class="nav-link" href="#timeline">Education</a>
</li>
<li class="nav-item position-relative">
<a class="nav-link" href="#portfolio">Portfolio</a>
</li>
<li class="nav-item position-relative">
<a class="nav-link" href="#contact">Contact</a>
</li>
</ul>
<a class="top-btn text-decoration-none d-inline-block" href="#">Download CV</a>
</div>
</div>
</nav>
what i try to do is when the user click on the link i want the whole meu to close and the user get the section he want
also if he click outside the menu the menu close if it's open
How to close the whole NavBar Menu when i click on a link inside or i click outside on the page?

<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<link href="https://cdn.jsdelivr.net/npm/bootstrap#5.0.0/dist/css/bootstrap.min.css" rel="stylesheet" >
<script src="https://cdn.jsdelivr.net/npm/#popperjs/core#2.9.2/dist/umd/popper.min.js" ></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap#5.0.1/dist/js/bootstrap.min.js" integrity="sha384-Atwg2Pkwv9vp0ygtn1JAojH0nYbwNJLPhwyoVbhoPwBhjQPR5VtM2+xf0Uwh9KtT" crossorigin="anonymous"></script>
</head>
<style></style>
<body>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<div class="container-fluid">
<a class="navbar-brand" href="#">Navbar</a>
<button
class="navbar-toggler"
type="button"
data-bs-toggle="collapse"
data-bs-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 me-auto mb-2 mb-lg-0">
<li class="nav-item dropdown">
<a
class="nav-link dropdown-toggle"
href="#"
id="navbarDropdown"
role="button"
data-bs-toggle="dropdown"
aria-expanded="false"
>
Dropdown
</a>
<ul class="dropdown-menu" aria-labelledby="navbarDropdown">
<li><a class="dropdown-item" href="#">Action</a></li>
<li><a class="dropdown-item" href="#">Another action</a></li>
<li><hr class="dropdown-divider" /></li>
<li>
<a class="dropdown-item" href="#">Something else here</a>
</li>
</ul>
</li>
</ul>
</div>
</div>
</nav>
</body>
<script
src="https://code.jquery.com/jquery-3.6.0.min.js"
integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4="
crossorigin="anonymous"
></script>
</html>

Bootstrap dropdown menu is not working[HTML]

i download bootstrap and added the scripts in my code, but don't know why. Everythig works fine, no error in console ,but a drop-down menu is not working ... what is the problem?
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<link rel="text/javascript" href="./assets/js/bootstrap.min.js">
<link rel="stylesheet" href="./assets/css/bootstrap.min.css">
<link rel="stylesheet" href="./assets/css/style.css">
<meta charset="utf-8">
</head>
<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>

It seems you almost got it right!
you have data-toggle it needs to be data-bs-toggle
that should fix it!
<head>
<link href="https://cdn.jsdelivr.net/npm/bootstrap#5.1.3/dist/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/bootstrap#5.1.3/dist/js/bootstrap.bundle.min.js"></script>
<meta charset="utf-8">
</head>
<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-bs-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>

Bootstrap 4 navbar nav-item active class not working

I am quite desperate, I checked every similar questions on stackoverflow and tried many solutions found on google but in vain... I'm really unable to find a working solution to my problem.
I am developping a site with Bootstrap 4 and I have a navbar. When I click on one of the nav-link I want it to have the "active" class, while others stay normal.
I might not select the right elements or use wrong jquery/javascript code.
The navbar html code (1) is in a separate header.html file that I load with JS at the beginning of the html page (2):
(1)
<nav class="navbar navbar-expand-lg navbar-dark bg-dark fixed-top ml-auto">
<div class="container">
<a class="navbar-brand" href="../index.html#"><img src="../images/DSIMB.svg" alt=""></a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarResponsive">
<ul class="navbar-nav ml-auto">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="" id="dropdown01" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Team</a>
<div class="dropdown-menu" aria-labelledby="dropdown01">
<a class="dropdown-item" href="members.html#">Members</a>
<a class="dropdown-item" href="publications.html#">Publications</a>
<a class="dropdown-item" href="teaching.html#">Teaching</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="web_tools.html#">Web Tools</a>
</li>
<li class="nav-item">
<a class="nav-link" href="research.html#">Research</a>
</li>
<li class="nav-item">
<a class="nav-link" href="infrastructures.html#">Infrastructures</a>
</li>
<li class="nav-item">
<a class="nav-link" href="news.html#">News</a>
</li>
<li class="nav-item">
<a class="nav-link" href="contacts.html#">Contacts</a>
</li>
</ul>
</div>
</div>
</nav>
(2)
<script>
$(function() {
$("#header").load("./header.html");
});
</script>
Here is the JS I put at the end of the html page just before the </body> tag:
<script>
$('.navbar .nav-item .navlink').click(function() {
$('.navbar .nav-item').removeClass('active');
$(this).addClass('active');
})
</script>
And here the active css class I want to set to the active nav-link:
.navbar .nav-item > .nav-link.active {
color:white;
font-weight: 700;
}
Please tell me what I am doing wrong...
UPDATE
I put here the solution I found thanks to a simple snippet (that I adapted to my code) taken from this site which #NmiDev kindly pointed to me.
I add my custom active class to the link in the navbar targeted thanks to href / location parsing:
$("#header").load("./header.html", function(){
$('a[href="' + location.pathname.split("/")[2] + '"]').addClass("active-nav");
});

Here a snippet.
Hope it's help you.
<!DOCTYPE html>
<html lang="en">
<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">
<title>Document</title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<style>
.active {
color: red !important;
}
</style>
</head>
<body>
<nav class="navbar navbar-expand-lg navbar-dark bg-dark fixed-top ml-auto">
<div class="container">
<a class="navbar-brand" href="../index.html#"><img src="../images/DSIMB.svg" alt=""></a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarResponsive">
<ul class="navbar-nav ml-auto">
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="" id="dropdown01" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Team</a>
<div class="dropdown-menu" aria-labelledby="dropdown01">
<a class="dropdown-item" href="#">Members</a>
<a class="dropdown-item" href="#">Publications</a>
<a class="dropdown-item" href="#">Teaching</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Web Tools</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Research</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Infrastructures</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">News</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Contacts</a>
</li>
</ul>
</div>
</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>
<script>
$('.nav-link').click(function() {
$('.nav-link').removeClass('active');
$(this).addClass('active');
})
</script>
</body>
</html>
It's seems that you don't need to override the css active class. White is the default behavior.

Bootstrap navbar dropdown menu/collapsed navbar not opening

I am trying to add a navbar to this website, but for some reason it is not functioning how I thought it would. The main problem I am trying to solve is getting the dropdown menu to actually display the list. It visually looks like the menu is already expanded, but I don't know if that has anything to do with why it is not working. Currently, the collapsed version will open from the hamburger menu only because of the CSS I added. Without the CSS, that navbar will expand, but immediately collapse again. Things I have tried:
I have tried to switch the order that I include Bootstrap.js/css and jQuery, but that has no effect on it.
I have also tried to switch versions because I am not sure what is compatible with what, but that has not been successful.
The one thing that did work was using an old version of bootstrap, but I would like to use 4.0 or higher if that is possible.
I would appreciate it is someone could help me figure out why this is not working. Thanks!
.navbar-collapse.collapse.in {
display: block!important;
}
<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<script
src="https://code.jquery.com/jquery-3.2.1.min.js">
</script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">
<link rel="stylesheet" href="index.css">
</head>
<body>
<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 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 dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Products
</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="#">About Us</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">Search</button>
</form>
</div>
</nav>
<div class="jumbotron">
<h1 class="display-3">Hello, world!</h1>
<p class="lead">This is a simple hero unit, a simple jumbotron-style component for calling extra attention to featured content or information.</p>
<hr class="my-4">
<p>It uses utility classes for typography and spacing to space content out within the larger container.</p>
<p class="lead">
<a class="btn btn-primary btn-lg" href="#" role="button">Learn more</a>
</p>
</div>
</body>
</html>

That's because your bootstrap.js is version 3.3.7, and this is not how you implement sub-menu (on bootstrap 3). Although, If you're using bootstrap 4 already, you should consider updating your bootstrap.js to version 4.0.0 (And you should use the same versions of bootstrap.js and bootstrap.css to avoid unexepected bugs (like you just had).
.navbar-collapse.collapse.in {
display: block!important;
}
<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<script
src="https://code.jquery.com/jquery-3.2.1.min.js">
</script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">
<link rel="stylesheet" href="index.css">
</head>
<body>
<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 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 dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Products
</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="#">About Us</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">Search</button>
</form>
</div>
</nav>
<div class="jumbotron">
<h1 class="display-3">Hello, world!</h1>
<p class="lead">This is a simple hero unit, a simple jumbotron-style component for calling extra attention to featured content or information.</p>
<hr class="my-4">
<p>It uses utility classes for typography and spacing to space content out within the larger container.</p>
<p class="lead">
<a class="btn btn-primary btn-lg" href="#" role="button">Learn more</a>
</p>
</div>
</body>
</html>

Bootstrap 4 Navbar Example Stuck in Mobile Mode

Right now I'm going to through the Bootstrap material and trying to learn how to use their content with a jinja2 file I'm prepping up for a django project. When I tried copy and pasting their example code
(specifically this example http://getbootstrap.com/docs/4.0/components/navbar/)
into my project it seemed to be working however none of the dropdown elements are responsive and when it enters mobile it wont expand. This was with me using my local css and js files, so I thought I'll use the recommended cdn files on the Jinja website. Now it is functional, but it is stuck in mobile mode. How should I resolve this problem?
Here's my source:
<!DOCTYPE html>
<html lang="en">
<head>
<title>My title</title>
<meta character="utf-8" />
{%load staticfiles %}
<!-- <link rel='stylesheet' href="{% static 'css/bootstrap.min.css'%}" type='text/css' media="screen" > -->
<!-- <script type="text/javascript" src="{% static 'js/bootstrap.min.js'%}"></script> -->
<script src="https://code.jquery.com/jquery-3.1.1.slim.min.js" integrity="sha384-A7FZj7v+d/sdmMqp/nOQwliLvUsJfDHW+k9Omg/a/EheAdgtzNs3hpfag6Ed950n" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js" integrity="sha384-DztdAPBWPRXSA/3eYEEUWrWCy7G5KFbe8fFjk5JAIxUYHKkDx6Qin1DkWx51bBrb" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js" integrity="sha384-vBWWzlZJ8ea9aCX4pEW3rVHjgjt7zpkNpZk+02D9phzyeVkE+jo0ieGizqPLForn" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">
</head>
<body class="body">
<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 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 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="#">Disabled</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">Search</button>
</form>
</div>
</nav>
<div>
{% block content%}
{% endblock %}
</div>
</body>
</html>

If you are using bootstrap V4.0.0-alpha.6,
Replace
navbar navbar-expand-lg navbar-light bg-light
with
navbar navbar-toggleable-md navbar-light bg-faded
Ref : https://v4-alpha.getbootstrap.com/components/navbar/
The link you added in your question is for bootstrap V4.0.0-beta.2 and in your code header files you added are for Bootstrap v4 alpha6
and you forgot to add JQuery in your code.
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" rel="stylesheet"/>
<body>
<nav class="navbar navbar-toggleable-md navbar-light bg-faded">
<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 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 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="#">Disabled</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">Search</button>
</form>
</div>
</nav>
</body>

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