load local bootstrap css and js if load fail from remote

Question

I'm trying to load local css & js file when remote file is not available. (wifi dis-connected) The major problem is "I don't know how to let css load proper". As I know jquery should put on bottom of body to reduce page load time. In browser's address line, I input localhost:8000//example.html (use a static web page web browser).

Demo Code

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <meta name="description" content="Go By Example - Google Go (golang) code examples" />
  <link rel="icon" href="favicon.ico">
  <title>Go by Example - Google Go (golang) code examples</title>
  <link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
  <link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap-theme.min.css">
</head>
  <body>
    <span class="glyphicon glyphicon-flash"></span>
    ...
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>!window.jQuery && document.write(unescape('%3Cscript src="js/jquery.min.js"%3E%3C/script%3E'))</script>
<script id="bsscript" src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<script>$("#bsscript").load("js/bootstrap.min.js")</script>

  </body>
</html>

Output error message of chromium

GET file://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css net::ERR_FILE_NOT_FOUND local.html:9
GET file://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap-theme.min.css net::ERR_FILE_NOT_FOUND local.html:10
GET http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js net::ERR_INTERNET_DISCONNECTED local.html:16
GET file://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js net::ERR_FILE_NOT_FOUND local.html:18

Try to check `if` the internet is accessible, then load the remote files. `Else` load the local files. That way, you can isolate the error to if the files themselves can be loaded or not. — Simple Sandman, Sep 09 '14 at 16:31
I don't know how to write the js for checking internet, and load css dynamic. — Daniel YC Lin, Sep 09 '14 at 23:26

Thibaud Granier · Accepted Answer · 2016-03-18T11:44:35.113

bootstrap cdn callback :

<head>
  <!-- Bootstrap CSS CDN -->
  <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css">
</head>
<body>
  <!-- APP CONTENT -->

  <!-- jQuery CDN -->
  <script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
  <!-- jQuery local fallback -->
  <script>window.jQuery || document.write('<script src="/local/jquery.min.js"><\/script>')</script>
  <!-- Bootstrap JS CDN -->
  <script src="//netdna.bootstrapcdn.com/bootstrap/3.0.3/js/bootstrap.min.js"></script>
  <!-- Bootstrap JS local fallback -->
  <script>if(typeof($.fn.modal) === 'undefined') {document.write('<script src="/local/bootstrap.min.js"><\/script>')}</script>
  <!-- Bootstrap CSS local fallback -->
  <script>
    $(document).ready(function() {
    var bodyColor = $('body').css('color');
    if(bodyColor != 'rgb(51, 51, 51)') {
    $("head").prepend('<link rel="stylesheet" href="/local/bootstrap.min.css">');}});
  </script>
</body>

Sergey Paukov · Answer 2 · 2018-01-10T17:23:13.743

and same in pureJS:(help,when jQuery is not availiable(Arduino etc..))

    <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css">
<script sync type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.1/Chart.min.js?modified=20012009"></script>

    <script>
        document.addEventListener('DOMContentLoaded', function () {
            var element = document.body,
                style = window.getComputedStyle(element),
                top = style.getPropertyValue('color');
            if (top!='rgb(51, 51, 51)'){
                var el = document.head,
                 elChild = document.createElement('link');
                elChild.innerHTML = '<link sync rel="stylesheet" href="bootstrap.min.css?modified=20012001">';
                el.insertBefore(elChild, el.firstChild);
            }
        if(isEmpty(Chart)){
            var tag = document.createElement("script");
            tag.src = "chart.min.js?modified=20012009";
            document.getElementsByTagName("head")[0].appendChild(tag);
        }

        })

    </script>

load local bootstrap css and js if load fail from remote

2 Answers2

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