Uncaught ReferenceError: $ is not defined Error - javascript

I am getting this err
Uncaught ReferenceError: $ is not defined.
I have searched and found that the usual cause of this is not having jQuery declared in the right place but I think I have it right.
Thanks in advance.
<script type="text/javascript" src="jquery-1.2.6.min.js"></script>
<script type="text/javascript" src="ajax2.js"></script>
<script type="text/javascript">
var slideimages = new Array() // create new array to preload images
slideimages[0] = new Image() // create new instance of image object
slideimages[0].src = "images/aib.jpg" // set image src property to image path, preloading image in the process
slideimages[1] = new Image()
slideimages[1].src = "images/paddypower.jpg"
slideimages[2] = new Image()
slideimages[2].src = "images/rtegaa.jpg"
slideimages[3] = new Image()
slideimages[3].src = "images/ssgaa.jpg"
$(document).ready(function(){
function get_weather()
{
var p = $("#code").val();
var u = ($('#u').attr('checked')) ? '&u=c' : '';
var to_load = 'get_weather.php?p='+ p + u;
$("#weather").html('<img style="margin-top: 104px;" src="ajax-loader.gif" align="absmiddle">');
$("#weather").load(to_load);
}
$(window).load(get_weather); // Trigger "get_weather" when the window loads
// Trigger "get_weather" when the form objects are used
$("#code").change(get_weather);
$("#u").click(get_weather);
});

The solution:
1) Use Google CDN to load jQuery
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js"></script>
2) It is compatible with jQuery v1.5-v1.7 because most of the methods were deprecated in jQuery 1.8+. This is the reason I've used v1.5 of Google CDN jquery in point 1. Most of the examples on cycle plugin use jquery 1.5.
3) Clear Your browser cache, It is the main culprit most of the times.
4) PLease check the loading of jquery using the code below
if(typeof jQuery!=='undefined'){
console.log('jQuery Loaded');
}
else{
console.log('not loaded yet');
}

Probably you called jQuery.noConflict() somewhere.
To solve this, wrap your code like this:
(function($, undefined){
if( !$ )
{
console.log('jQuery failed to load');
return;
}
//jquery code here
})(window.jQuery);
This will prevent the jQuery.noConflict() from affecting your code and you can debug in case jQuery is having some troubles.
Also, watch your 'Network' tab, on the Element Inspector (press F12).

This error will not occur if the file "jquery-1.2.6.min.js" is not present in the location mentioned in your script tag. From your code, the jquery file should be present in the same folder as your startup page.
I'll check the following things when this error occurs
1) Make sure the jquery script file is present in the correct location
2) Name of the jquery file is same as referenced in script tag
3) In browsers console window, there is a debugger or source tab which shows all the script and CSS files used by the page. Check jquery is present under the sources tab of the browser

Related

When injecting an HTML template with a Google Chrome extension with various scripts, jQuery doesn't seem to import

To elaborate, I am injecting and loading an HTML template in my Google Chrome extension like this:
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
// Typical action to be performed when the document is ready:
var PBSKPage = xhttp.responseText;
document.querySelector('html').innerHTML = "";
loadPBSKPage();
function loadPBSKPage() {
document.querySelector('html').innerHTML = PBSKPage;
}
}
};
function insertAndExecute() {
var scripts = Array.prototype.slice.call(document.getElementsByTagName("script"));
for (var i = 0; i < scripts.length; i++) {
if (scripts[i].src != "") {
var tag = document.createElement("script");
tag.src = scripts[i].src;
document.getElementsByTagName("head")[0].appendChild(tag);
}
else {
eval(scripts[i].innerHTML);
}
}
}
And in my HTML template, I clearly put the script tag that requests jQuery before the jQuery-reliant scripts:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="chrome-extension://niabfndainielhgpcjenbpodannhfofj/2015/pbsk_resources/wildkratts/js/vendor/jquery-1.11.0.min.js"><\/script>')</script>
<script src="chrome-extension://niabfndainielhgpcjenbpodannhfofj/2015/pbsk_resources/wildkratts/js/vendor/jquery.nivo.slider.pack.js" type="text/javascript"></script>
<script src="chrome-extension://niabfndainielhgpcjenbpodannhfofj/2015/pbsk_resources/wildkratts/js/vendor/jquery.touchSwipe.min.js" type="text/javascript"></script>
<script src="chrome-extension://niabfndainielhgpcjenbpodannhfofj/2015/pbsk_resources/wildkratts/js/vendor/retina.min.js"></script>
...
jQuery doesn't seem to import, and when the JS files are executed, the browser always spits out an Uncaught TypeError on something that would be defined if jQuery was imported.
So what do I do? Is this because of CSP? Is it because of the insertAndExecute() function? Is it because of the intrinsic inner workings of Google Chrome extensions? I suppose I could just paste the jQuery JS into each of the jQuery-reliant JS files, but that wouldn't be very efficient. Does anyone have a solution to this?
I don't have a high enough rep to comment on the answer above mine, but bundling jQuery with your code and the libraries you wish to use should do the trick. That said, it might be a good idea to use a more up-to-date version of jQuery since it's received a number of significant security patches since version 1.11.
Yes this is an issue with the CSP as chrome does not want people to link external libraries and change them later maliciously or not. You can get the jQuery library and add it to your project explicitly but yes it is more work :(

How to include jquery online version, or fall back to offline if not available [duplicate]

What would be a good way to attempt to load the hosted jQuery at Google (or other Google hosted libs), but load my copy of jQuery if the Google attempt fails?
I'm not saying Google is flaky. There are cases where the Google copy is blocked (apparently in Iran, for instance).
Would I set up a timer and check for the jQuery object?
What would be the danger of both copies coming through?
Not really looking for answers like "just use the Google one" or "just use your own." I understand those arguments. I also understand that the user is likely to have the Google version cached. I'm thinking about fallbacks for the cloud in general.
Edit: This part added...
Since Google suggests using google.load to load the ajax libraries, and it performs a callback when done, I'm wondering if that's the key to serializing this problem.
I know it sounds a bit crazy. I'm just trying to figure out if it can be done in a reliable way or not.
Update: jQuery now hosted on Microsoft's CDN.
http://www.asp.net/ajax/cdn/
You can achieve it like this:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
<script>
window.jQuery || document.write('<script src="/path/to/your/jquery"><\/script>');
</script>
This should be in your page's <head> and any jQuery ready event handlers should be in the <body> to avoid errors (although it's not fool-proof!).
One more reason to not use Google-hosted jQuery is that in some countries, Google's domain name is banned.
The easiest and cleanest way to do this by far:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="path/to/your/jquery"><\/script>')</script>
This seems to work for me:
<html>
<head>
<script type="text/javascript" src="http://www.google.com/jsapi"></script>
<script type="text/javascript">
// has the google object loaded?
if (window.google && window.google.load) {
google.load("jquery", "1.3.2");
} else {
document.write('<script type="text/javascript" src="http://joecrawford.com/jquery-1.3.2.min.js"><\/script>');
}
window.onload = function() {
$('#test').css({'border':'2px solid #f00'});
};
</script>
</head>
<body>
<p id="test">hello jQuery</p>
</body>
</html>
The way it works is to use the google object that calling http://www.google.com/jsapi loads onto the window object. If that object is not present, we are assuming that access to Google is failing. If that is the case, we load a local copy using document.write. (I'm using my own server in this case, please use your own for testing this).
I also test for the presence of window.google.load - I could also do a typeof check to see that things are objects or functions as appropriate. But I think this does the trick.
Here's just the loading logic, since code highlighting seems to fail since I posted the whole HTML page I was testing:
if (window.google && window.google.load) {
google.load("jquery", "1.3.2");
} else {
document.write('<script type="text/javascript" src="http://joecrawford.com/jquery-1.3.2.min.js"><\/script>');
}
Though I must say, I'm not sure that if this is a concern for your site visitors you should be fiddling with the Google AJAX Libraries API at all.
Fun fact: I tried initially to use a try..catch block for this in various versions but could not find a combination that was as clean as this. I'd be interested to see other implementations of this idea, purely as an exercise.
If you have modernizr.js embedded on your site, you can use the built-in yepnope.js to load your scripts asynchronously - among others jQuery (with fallback).
Modernizr.load([{
load : '//ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js'
},{
test : window.jQuery,
nope : 'path/to/local/jquery-1.7.2.min.js',
both : ['myscript.js', 'another-script.js'],
complete : function () {
MyApp.init();
}
}]);
This loads jQuery from the Google-cdn. Afterwards it's checked, if jQuery was loaded successfully. If not ("nope"), the local version is loaded. Also your personal scripts are loaded - the "both" indicates, that the load-process is iniated independently from the result of the test.
When all load-processes are complete, a function is executed, in the case 'MyApp.init'.
I personally prefer this way of asynchronous script loading. And as I rely on the feature-tests provided by modernizr when building a site, I have it embedded on the site anyway. So there's actually no overhead.
There are some great solutions here, but I'll like to take it one step further regarding the local file.
In a scenario when Google does fail, it should load a local source but maybe a physical file on the server isn't necessarily the best option. I bring this up because I'm currently implementing the same solution, only I want to fall back to a local file that gets generated by a data source.
My reasons for this is that I want to have some piece of mind when it comes to keeping track of what I load from Google vs. what I have on the local server. If I want to change versions, I'll want to keep my local copy synced with what I'm trying to load from Google. In an environment where there are many developers, I think the best approach would be to automate this process so that all one would have to do is change a version number in a configuration file.
Here's my proposed solution that should work in theory:
In an application configuration file, I'll store 3 things: absolute URL for the library, the URL for the JavaScript API, and the version number
Write a class which gets the file contents of the library itself (gets the URL from app config), stores it in my datasource with the name and version number
Write a handler which pulls my local file out of the db and caches the file until the version number changes.
If it does change (in my app config), my class will pull the file contents based on the version number, save it as a new record in my datasource, then the handler will kick in and serve up the new version.
In theory, if my code is written properly, all I would need to do is change the version number in my app config then viola! You have a fallback solution which is automated, and you don't have to maintain physical files on your server.
What does everyone think? Maybe this is overkill, but it could be an elegant method of maintaining your AJAX libraries.
Acorn
if (typeof jQuery == 'undefined') {
// or if ( ! window.jQuery)
// or if ( ! 'jQuery' in window)
// or if ( ! window.hasOwnProperty('jQuery'))
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = '/libs/jquery.js';
var scriptHook = document.getElementsByTagName('script')[0];
scriptHook.parentNode.insertBefore(script, scriptHook);
}
After you attempt to include Google's copy from the CDN.
In HTML5, you don't need to set the type attribute.
You can also use...
window.jQuery || document.write('<script src="/libs/jquery.js"><\/script>');
You might want to use your local file as a last resort.
Seems as of now jQuery's own CDN does not support https. If it did you then might want to load from there first.
So here's the sequence:
Google CDN =>
Microsoft CDN =>
Your local copy.
<!-- load jQuery from Google's CDN -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<!-- fallback to Microsoft's Ajax CDN -->
<script> window.jQuery || document.write('<script src="//ajax.aspnetcdn.com/ajax/jQuery/jquery-1.8.3.min.js">\x3C/script>')</script>
<!-- fallback to local file -->
<script> window.jQuery || document.write('<script src="Assets/jquery-1.8.3.min.js">\x3C/script>')</script>
Conditionally load latest/legacy jQuery version and fallback:
<!--[if lt IE 9]>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="/public/vendor/jquery-legacy/dist/jquery.min.js">\x3C/script>')</script>
<![endif]-->
<!--[if gte IE 9]><!-->
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="/public/vendor/jquery/dist/jquery.min.js">\x3C/script>')</script>
<!--<![endif]-->
Step 1: Did jQuery fail to load? (check jQuery variable)
How to check a not-defined variable in JavaScript
Step 2: Dynamically import (the backup) javascript file
How do I include a JavaScript file in another JavaScript file?
Because of the Google's banning problem I prefer to use Microsoft's cdn
http://www.asp.net/ajaxlibrary/cdn.ashx
For those people using ASP.NET MVC 5, add this code in your BundleConfig.cs to enable the CDN for jquery:
bundles.UseCdn = true;
Bundle jqueryBundle = new ScriptBundle("~/bundles/jquery", "//ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js").Include("~/Scripts/jquery-{version}.js");
jqueryBundle.CdnFallbackExpression = "window.jQuery";
bundles.Add(jqueryBundle);
UPDATE:
This answer turned out to be wrong. Please see the comments for the real explanation.
Most of you question has been answered, but as for the final part:
What would be the danger of both copies coming through?
None really. You'd waste bandwidth, might add some milliseconds downloading a second useless copy, but there's not actual harm if they both come through. You should, of course, avoid this using the techniques mentioned above.
I made a Gist that should dynamically load jQuery if it isn't already loaded, and if the source fails, it proceeds onto fallbacks (stitched together from many answers): https://gist.github.com/tigerhawkvok/9673154
Please note I plan to keep the Gist updated but not this answer, for what it's worth!
/* See https://gist.github.com/tigerhawkvok/9673154 for the latest version */
function cascadeJQLoad(i) { // Use alternate CDNs where appropriate to load jQuery
if (typeof(i) != "number") i = 0;
// the actual paths to your jQuery CDNs
var jq_paths = [
"ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js",
"ajax.aspnetcdn.com/ajax/jQuery/jquery-2.1.0.min.js"
];
// Paths to your libraries that require jQuery
var dependent_libraries = [
"js/c.js"
];
if (window.jQuery === undefined && i < jq_paths.length) {
i++;
loadJQ(jq_paths[i], i, dependent_libraries);
}
if (window.jQuery === undefined && i == jq_paths.length) {
// jQuery failed to load
// Insert your handler here
}
}
/***
* You shouldn't have to modify anything below here
***/
function loadJQ(jq_path, i, libs) { //load jQuery if it isn't already
if (typeof(jq_path) == "undefined") return false;
if (typeof(i) != "number") i = 1;
var loadNextJQ = function() {
var src = 'https:' == location.protocol ? 'https' : 'http';
var script_url = src + '://' + jq_path;
loadJS(script_url, function() {
if (window.jQuery === undefined) cascadeJQLoad(i);
});
}
window.onload = function() {
if (window.jQuery === undefined) loadNextJQ();
else {
// Load libraries that rely on jQuery
if (typeof(libs) == "object") {
$.each(libs, function() {
loadJS(this.toString());
});
}
}
}
if (i > 0) loadNextJQ();
}
function loadJS(src, callback) {
var s = document.createElement('script');
s.src = src;
s.async = true;
s.onreadystatechange = s.onload = function() {
var state = s.readyState;
try {
if (!callback.done && (!state || /loaded|complete/.test(state))) {
callback.done = true;
callback();
}
} catch (e) {
// do nothing, no callback function passed
}
};
s.onerror = function() {
try {
if (!callback.done) {
callback.done = true;
callback();
}
} catch (e) {
// do nothing, no callback function passed
}
}
document.getElementsByTagName('head')[0].appendChild(s);
}
/*
* The part that actually calls above
*/
if (window.readyState) { //older microsoft browsers
window.onreadystatechange = function() {
if (this.readyState == 'complete' || this.readyState == 'loaded') {
cascadeJQLoad();
}
}
} else { //modern browsers
cascadeJQLoad();
}
Google Hosted jQuery
If you care about older browsers, primarily versions of IE prior to IE9, this is the most widely compatible jQuery version
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
If you don’t care about oldIE, this one is smaller and faster:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
Backup/Fallback Plan!
Either way, you should use a fallback to local just in case the Google CDN fails (unlikely) or is blocked in a location that your users access your site from (slightly more likely), like Iran or sometimes China.
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>if (!window.jQuery) { document.write('<script src="/path/to/your/jquery"><\/script>'); }
</script>
Reference: http://websitespeedoptimizations.com/ContentDeliveryNetworkPost.aspx
I consider that should escape the last < to \x3C in string. When the browser sees , it considers this to be the end of the script block (since the HTML parser has no idea about JavaScript, it can't distinguish between something that just appears in a string, and something that's actually meant to end the script element). So appearing literally in JavaScript that's inside an HTML page will (in the best case) cause errors, and (in the worst case) be a huge security hole.
<script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-2.0.0.min.js"></script>
<script>window.jQuery || document.write('<script src="js/jquery-2.0.0.min.js">\x3C/script>')</script>
if (typeof jQuery == 'undefined')) { ...
Or
if(!window.jQuery){
Will not works if cdn version not loaded, because browser will run through this condition and during it still downloading the rest of javascripts which needs jQuery and it returns error. Solution was to load scripts through that condition.
<script src="http://WRONGPATH.code.jquery.com/jquery-1.4.2.min.js" type="text/javascript"></script><!-- WRONGPATH for test-->
<script type="text/javascript">
function loadCDN_or_local(){
if(!window.jQuery){//jQuery not loaded, take a local copy of jQuery and then my scripts
var scripts=['local_copy_jquery.js','my_javascripts.js'];
for(var i=0;i<scripts.length;i++){
scri=document.getElementsByTagName('head')[0].appendChild(document.createElement('script'));
scri.type='text/javascript';
scri.src=scripts[i];
}
}
else{// jQuery loaded can load my scripts
var s=document.getElementsByTagName('head')[0].appendChild(document.createElement('script'));
s.type='text/javascript';
s.src='my_javascripts.js';
}
}
window.onload=function(){loadCDN_or_local();};
</script>
Almost all public CDNs are pretty reliably. However, if you are worried about blocked google domain, then you can simply fallback to an alternative jQuery CDN. However, in such a case, you may prefer to do it opposite way and use some other CDN as your preferred option and fallback to Google CDN to avoid failed requests and waiting time:
<script src="https://pagecdn.io/lib/jquery/3.2.1/jquery.min.js"></script>
<script>
window.jQuery || document.write('<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"><\/script>');
</script>
Using Razor syntax in ASP.NET, this code provides fallback support and works with a virtual root:
#{var jQueryPath = Url.Content("~/Scripts/jquery-1.7.1.min.js");}
<script type="text/javascript">
if (typeof jQuery == 'undefined')
document.write(unescape("%3Cscript src='#jQueryPath' type='text/javascript'%3E%3C/script%3E"));
</script>
Or make a helper (helper overview):
#helper CdnScript(string script, string cdnPath, string test) {
#Html.Raw("<script src=\"http://ajax.aspnetcdn.com/" + cdnPath + "/" + script + "\" type=\"text/javascript\"></script>" +
"<script type=\"text/javascript\">" + test + " || document.write(unescape(\"%3Cscript src='" + Url.Content("~/Scripts/" + script) + "' type='text/javascript'%3E%3C/script%3E\"));</script>")
}
and use it like this:
#CdnScript("jquery-1.7.1.min.js", "ajax/jQuery", "window.jQuery")
#CdnScript("jquery.validate.min.js", "ajax/jquery.validate/1.9", "jQuery.fn.validate")
Although writing document.write("<script></script>") seems easier for jQuery backoff, Chrome gives validation error on that case. So I prefer breaking "script" word. So it becomes safer like above.
<script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.11.1.min.js"></script>
<script>if (typeof jQuery === "undefined") {
window.jqFallback = true;
document.write("<scr"+"ipt src='http://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.1/jquery.min.js'></scr"+"ipt>");
} </script>
For long term issues, it would be better to log JQuery fallbacks. In the code above, if first CDN is not available JQuery is loaded from another CDN. But you could want to know that erroneous CDN and remove it permanently. (this case is very exceptional case) Also it is better to log fallback issues. So you can send erroneous cases with AJAX. Because of JQuery isn't defined, you should use vanilla javascript for AJAX request.
<script type="text/javascript">
if (typeof jQuery === 'undefined' || window.jqFallback == true) {
// XMLHttpRequest for IE7+, Firefox, Chrome, Opera, Safari
// ActiveXObject for IE6, IE5
var xmlhttp = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
var url = window.jqFallback == true ? "/yourUrl/" : "/yourUrl2/";
xmlhttp.open("POST", url, true);
xmlhttp.send();
}
</script>
The inability to load the resource from an external data store beyond your control is difficult. Looking for missing functions is totally fallacious as a means to avoid suffering a timeout, as described herein:
http://www.tech-101.com/support/topic/4499-issues-using-a-cdn/
Yet another fallback that replaces ajax.googleapis.com with cdnjs.cloudflare.com:
(function (doc, $)
{
'use strict';
if (typeof $ === 'undefined')
{
var script = doc.querySelector('script[src*="jquery.min.js"]'),
src = script.src.replace('ajax.googleapis.com', 'cdnjs.cloudflare.com');
script.parentNode.removeChild(script);
doc.write('<script src="' + src + '"></script>');
}
})(document, window.jQuery || window.Zepto);
You can stick to a jQuery version by specifying it in the string
Perfect for Asset Management that doesn't work with HTML snips
Tested in the wild - works perfect for users from China
You can use code like:
<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>
<script>window.jQuery || document.write('<script type="text/javascript" src="./scripts/jquery.min.js">\x3C/script>')</script>
But also there are libraries you can use to setup several possible fallbacks for your scripts and optimize the loading process:
basket.js
RequireJS
yepnope
Examples:
basket.js
I think the best variant for now. Will cach your script in the localStorage, that will speed up next loadings. The simplest call:
basket.require({ url: '/path/to/jquery.js' });
This will return a promise and you can do next call on error, or load dependencies on success:
basket
.require({ url: '/path/to/jquery.js' })
.then(function () {
// Success
}, function (error) {
// There was an error fetching the script
// Try to load jquery from the next cdn
});
RequireJS
requirejs.config({
enforceDefine: true,
paths: {
jquery: [
'//ajax.aspnetcdn.com/ajax/jquery/jquery-2.0.0.min',
//If the CDN location fails, load from this location
'js/jquery-2.0.0.min'
]
}
});
//Later
require(['jquery'], function ($) {
});
yepnope
yepnope([{
load: 'http://ajax.aspnetcdn.com/ajax/jquery/jquery-2.0.0.min.js',
complete: function () {
if (!window.jQuery) {
yepnope('js/jquery-2.0.0.min.js');
}
}
}]);
You should never need to use a personal copy. Here is my full belt and braces script.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8"/>
<title>jQuery</title>
<!-- EMBED JQUERY USING GOOGLE APIs -->
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<!-- IF THAT FAILS EMBED JQUERY USING CLOUDFLARE CDN -->
<script type="text/javascript">
window.jQuery || document.write('<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"><\/script>');
</script>
<!-- IF THAT FAILS ************* HOW??? *********** EMBED JQUERY FROM MICROSOFT -->
<script type="text/javascript">
window.jQuery || document.write('<script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.6.0.min.js"><\/script>');
</script>
<!-- IF THAT FAILS ************* WOW!!! *********** EMBED JQUERY FROM JQUERY.COM -->
<script type="text/javascript">
window.jQuery || document.write('<script src="https://code.jquery.com/jquery-3.6.0.min.js"><\/script>');
</script>
<!-- IF THAT FAILS ************* LET'S STOP!!! *********** EMBED JQUERY FROM PERSONAL COPY -->
<script type="text/javascript">
window.jQuery || document.write('<script src="jquery.min.js"><\/script>');
</script>
</head>
<body>
</body>
</html>

How to detect if any of css/js files failed to load and alert user to refresh browser [duplicate]

I have an HTML page where several JavaScript, CSS and images files are referenced. These references are dynamically injected and user can manually copy the HTML page and the support files to another machine.
If some JS or CSS are missing, the browser complains in the console. For example:
Error GET file:///E:/SSC_Temp/html_005/temp/Support/jquery.js
I need somehow these errors reported back to me on the inline JavaScript of the HTML page so I can ask user to first verify that support files are copied correctly.
There's the window.onerror event which just inform me that there's a JS error on the page such as an Unexpected Syntax error, but this doesn't fire in the event of a 404 Not Found error. I want to check for this condition in case of any resource type, including CSS, JS, and images.
I do not like to use jQuery AJAX to verify that file physically exists - the I/O overhead is expensive for every page load.
The error report has to contain the name of the file missing so I can check if the file is core or optional.
Any Ideas?
To capture all error events on the page, you can use addEventListener with the useCapture argument set to true. The reason window.onerror will not do this is because it uses the bubble event phase, and the error events you want to capture do not bubble.
If you add the following script to your HTML before you load any external content, you should be able to capture all the error events, even when loading offline.
<script type="text/javascript">
window.addEventListener('error', function(e) {
console.log(e);
}, true);
</script>
You can access the element that caused the error through e.target. For example, if you want to know what file did not load on an img tag, you can use e.target.src to get the URL that failed to load.
NOTE: This technically will not detect the error code, it detects if the image failed to load, as it technically behaves the same regardless of the status code. Depending on your setup this would probably be enough, but for example if a 404 is returned with a valid image it will not trigger an error event.
you can use the onload and onerror attributes to detect the error
for example upon loading the following html it gives alert error1 and error2 you can call your own function e.g onerror(logError(this);) and record them in an Array and once the page is fully loaded post is with single Ajax call.
<html>
<head>
<script src="file:///SSC_Temp/html_005/temp/Support/jquery.js" onerror="alert('error1');" onload="alert('load');" type="text/javascript" ></script>
</head>
<body>
<script src="file:///SSC_Temp/html_005/temp/Support/jquery.js" onerror="alert('error2');" onload="alert('load');" type="text/javascript" ></script>
</body>
</html>
I've put together the code below in pure JavaScript, tested, and it works.
All the source code (html, css, and Javascript) + images and example font is here: on github.
The first code block is an object with methods for specific file extensions: html and css.
The second is explained below, but here is a short description.
It does the following:
the function check_file takes 2 arguments: a string path and a callback function.
gets the contents of given path
gets the file extension (ext) of the given path
calls the srcFrom [ext] object method that returns an array of relative paths that was referenced in the string context by src, href, etc.
makes a synchronous call to each of these paths in the paths array
halts on error, and returns the HTTP error message and the path that had a problem, so you can use it for other issues as well, like 403 (forbidden), etc.
For convenience, it resolves to relative path names and does not care about which protocol is used (http or https, either is fine).
It also cleans up the DOM after parsing the CSS.
var srcFrom = // object
{
html:function(str)
{
var prs = new DOMParser();
var obj = prs.parseFromString(str, 'text/html');
var rsl = [], nds;
['data', 'href', 'src'].forEach(function(atr)
{
nds = [].slice.call(obj.querySelectorAll('['+atr+']'));
nds.forEach(function(nde)
{ rsl[rsl.length] = nde.getAttribute(atr); });
});
return rsl;
},
css:function(str)
{
var css = document.createElement('style');
var rsl = [], nds, tmp;
css.id = 'cssTest';
css.innerHTML = str;
document.head.appendChild(css);
css = [].slice.call(document.styleSheets);
for (var idx in css)
{
if (css[idx].ownerNode.id == 'cssTest')
{
[].slice.call(css[idx].cssRules).forEach(function(ssn)
{
['src', 'backgroundImage'].forEach(function(pty)
{
if (ssn.style[pty].length > 0)
{
tmp = ssn.style[pty].slice(4, -1);
tmp = tmp.split(window.location.pathname).join('');
tmp = tmp.split(window.location.origin).join('');
tmp = ((tmp[0] == '/') ? tmp.substr(1) : tmp);
rsl[rsl.length] = tmp;
}
});
});
break;
}
}
css = document.getElementById('cssTest');
css.parentNode.removeChild(css);
return rsl;
}
};
And here is the function that gets the file contents and calls the above object method according to the file extension:
function check_file(url, cbf)
{
var xhr = new XMLHttpRequest();
var uri = new XMLHttpRequest();
xhr.open('GET', url, true);
xhr.onload = function()
{
var ext = url.split('.').pop();
var lst = srcFrom[ext](this.response);
var rsl = [null, null], nds;
var Break = {};
try
{
lst.forEach(function(tgt)
{
uri.open('GET', tgt, false);
uri.send(null);
if (uri.statusText != 'OK')
{
rsl = [uri.statusText, tgt];
throw Break;
}
});
}
catch(e){}
cbf(rsl[0], rsl[1]);
};
xhr.send(null);
}
To use it, simply call it like this:
var uri = 'htm/stuff.html'; // html example
check_file(uri, function(err, pth)
{
if (err)
{ document.write('Aw Snap! "'+pth+'" is missing !'); }
});
Please feel free to comment and edit as you wish, i did this is a hurry, so it may not be so pretty :)
#alexander-omara gave the solution.
You can even add it in many files but the window handler can/should be added once.
I use the singleton pattern to achieve this:
some_global_object = {
error: (function(){
var activate = false;
return function(enable){
if(!activate){
activate = true;
window.addEventListener('error', function(e){
// maybe extra code here...
// if(e.target.custom_property)
// ...
}, true);
}
return activate;
};
}());
Now, from any context call it as many times you want as the handler is attached only once:
some_global_object.error();

How can I make HTML5 imports work properly on Firefox and IE11

I'm using some features of the Web Platform such HTML Imports.
On Chrome 52, everything works fine, as expected. I know that there are issues with HTML Imports on IE11 and FF 47.
However I've been requested to deploy my web app on IE-11 for some users. And here begins the pain. As suggested by the few articles one can find on internet, I called webcomponents polyfills in the head of my index.html, which is the "importer" file:
<script src="//cdnjs.cloudflare.com/ajax/libs/polymer/0.3.3/platform.js"></script>
Also in the head itself:
<meta http-equiv="X-UA-Compatible" content="IE=Edge;FF=3;OtherUA=4" />
The code to instantiate the link selector, with dynamic content based on the app state:
var link = document.createElement('link');
link.rel = 'import';
link.href=ubicacion;
link.onload = function(e) {console.log('Loaded import: ' + e.target.href);};
link.onerror = function(e) {'Error loading import: ' + e.target.href};
document.head.appendChild(link);
And when loading on IE-11 I get threee error messages in console:
Loaded Import: https://www.example.com/import.html
SCRIPT5007: Can't get 'querySelector' property of null reference or undefined.
Can't set property 'innerHTML' of reference null or undefined.
At the end of the index.html file, I put the following code:
var div = document.getElementById('vista');
var view = document.querySelector('link[rel="import"]');
var content = view.import;
var el = content.querySelector('.view');
div.appendChild(el.cloneNode(true));
The funny thing is that the polyfill works, because the onload message is printed instead of the onerror. However there is an issue when getting the content of the "imported" file:
var el = content.querySelector('.view');
Which by the way has the following code at the beginning:
<div class="view" >
<script >
document._currentScript = document._currentScript || document.currentScript;
var importDoc = document.currentScript.ownerDocument;
var mainDoc = document;
As I stated before, this works fine on Chrome. The problem is on IE-11 and even on Firefox 47. Even in FF I enabled the dom.webcomponents.enabled to true.
What can be improved in order to make HTML5 imports work fine on IE-11 and FF-47.
Please note that the users require IE-11, Edge is not a possibility.
I appreciate your answers relating to vanillajs. I'm not using jquery or any js wrapper. Thanks.
Your problem is that you are attempting to access a property before its defined.
var content = view.import;
The import property will be null until the webcomponents polyfill traverses the DOM and upgrades the link tag. You need to wrap that in a handler like so:
document.addEventListener('WebComponentsReady', function(e) {
var div = document.getElementById('vista');
var view = document.querySelector('link[rel="import"]');
var content = view.import;
var el = content.querySelector('.view'); // should be good now.
});
Docs regarding the .import property.

Dynamically accessing changing variable from external .js file

I'm very new to javascript (c++ normally) and I think this question should be quite basic for you all.
I have a script that gets a variable defined in an external .js file and displays it using an alert.
The code in the .html file looks like this.
<html>
<head>
<title></title>
<script>
function addScript(url){
var extScript = document.createElement('script');
extScript.type = 'text/javascript';
extScript.src = url;
extScript.id = 'extScript'
//If there is already a script with the ID 'extScript'
//get rid of it
var headList = document.getElementsByTagName('head');
var scriptList = headList[0].getElementsByTagName('script');
for(var i = 0; i < scriptList.length; i++)
{
if(scriptList[i].id =='extScript')
{
document.getElementsByTagName('head')[0].removeChild(scriptList[i]);
}
}
document.getElementsByTagName('head')[0].appendChild(extScript);
}
function newNewChangeMode()
{
addScript("C:/Users/Suzaku/Documents/Javascript/controller.js");
alert("Neo controllerMode variable is reading " + controllerMode);
}
</script>
</head>
<body>
Get externally defined mode
</body>
</html>
And the file "controller.js" looks like this.
var controllerMode = 1111;
(that's it!)
When I click the link "get externally defined mode", my javascript runs and the alert is displayed correctly. Displaying "Neo controllerMode variable is reading 1111".
However, if I change the variable controllerMode's definition (in controller.js) to
var controllerMode = 2222;
,hit save, and click the the button again (without refreshing), it still alerts "Neo controllerMode variable is reading 1111". Whereas it SHOULD say "Neo controllerMode variable is reading 2222".
It would seem that this script is not being added dynamically. I need to be able to change this variable without having to refresh the .html.
Thanks in advance,
Guy
It sounds like your browser is only retrieving the cached javascript file. Make sure you go directly to your updated javascript file (controller.js) and hit F5 to ENSURE that you are loading a new version, not the cached one. Otherwise your browser will keep plugging the old, cached script (which has 1111 defined) into your script. Common problem!

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