JS - Variable detection across files [duplicate] - javascript

This question already has answers here:
Best way to use Google's hosted jQuery, but fall back to my hosted library on Google fail
(23 answers)
Closed 8 years ago.
I’m using a CDN for the following javascript:
https://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js
https://ajax.googleapis.com/ajax/libs/jqueryui/1.8.10/jquery-ui.min.js
http://ajax.aspnetcdn.com/ajax/mvc/3.0/jquery.validate.unobtrusive.min.js
http://ajax.aspnetcdn.com/ajax/jquery.validate/1.7/jquery.validate.min.js
For each one, how can I revert to using local copy in the instance where it may be blocked/unavailable?

To confirm that cdn script loaded you can check for existence any variable/function this script defines, if it is undefined - then cdn failed and you need to load local script copy.
On this principle are based solutions like that:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/libs/jquery-1.5.1.min.js">\x3C/script>')</script>
(if there is no window.jQuery property defined cdn script didn't loaded).
You may build your own solutions using this method. For instance, jquery tooltip plugin creates $.tooltip() function so we can check it with code like this:
<script>
if (typeof $.tooltip === 'undefined') {
document.write('<script src="js/libs/jquery.tooltip.min.js">\x3C/script>');
}
</script>

I would have looked into a plugin like yepnopejs
yepnope([{
load: 'http:/­/ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js',
complete: function () {
if (!window.jQuery) {
yepnope('local/jquery.min.js');
}
}
}]);
Takes an array of object to check for, check the documentation at the site

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.js"></script>
<script>!window.jQuery && document.write(unescape('%3Cscript src="js/libs/jquery-1.4.2.js"%3E%3C/script%3E'))</script>
Taken from HTML5 Boilerplate.

I use http://fallback.io/
fallback.load({
// Include your stylesheets, this can be an array of stylesheets or a string!
page_css: 'index.css',
// JavaScript library. THE KEY MUST BE THE LIBARIES WINDOW VARIABLE!
JSON: '//cdnjs.cloudflare.com/ajax/libs/json2/20121008/json2.min.js',
// Here goes a failover example. The first will fail, therefore Fallback JS will load the second!
jQuery: [
'//ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.FAIL_ON_PURPOSE.min.js',
'//ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js',
'//cdnjs.cloudflare.com/ajax/libs/jquery/1.9.0/jquery.min.js'
], .......

first thing - shouldn't you include them in different order?
something like this should work:
<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.7/jquery.validate.min.js"></script>
<script src="http://ajax.aspnetcdn.com/ajax/mvc/3.0/jquery.validate.unobtrusive.min.js"></script>
<script>jQuery.fn.validate || document.write('<script src="js/jquery.validate.min.js">\x3C/script><script src="js/jquery.validate.unobtrusive.min.js">\x3C/script>'</script>
what I'm doing here is simply checking if the first plugin (jQ validate) has been loaded. by checking for a static validate function on jQuery.fn object. I can't check the second script same way, because it's not adding anything anywhere, just proxying existing methods, so it's easier to assume that if the first one works, the second one will work too - after all, they are provided by the same CDN.

You need to know, how you can make sure that a lib was loaded successfully. For instance:
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.js"></script>
<script>window.jQuery || document.write('<script src="js/jquery.min.js">\x3C/script>'</script>
So this trys to load jQuery (1.5.1) from the google CDN. Since <script> tags do block the overall render & execution process (if not explicitly told different), we can check right after that if the jQuery object is found within window. If not, just fallback by writing another <script> tag into the document, referencing a local copy.

The following solution passes validation for both HTML5, XHTML 1.0 Transitional and other HTML flavors. Place the following after each of your external JQuery call. Be sure to replace jquery.min.js with the path to your local copy of the JQuery script.
<script type="application/javascript">window.jQuery ||
document.write(unescape('%3Cscript src="jquery.min.js"%3E%3C/script%3E'))</script>
If you don't use unescape, you'll have errors when validating with http://validator.w3.org since "%" is not allowed in an attribute specification list.
The HTML5 Boilerplate example also has validation errors when used with older HTML:
required attribute "type" not specified
character "&" is the first character of a delimiter but occurred as data
You'll be fine with the HTML5 Boilerplate solution if you are developing only for HTML5 and future HTML flavors, but since you may find yourself inserting portions of your code into legacy HTML, play it safe with this one-size-fits-all approach.
You'll need to specify a different function for each externally hosted script. For instance, the JQuery Tooltip plugin creates the $.tooltip() function, so you can check it with the following:
<script type="application/javascript">typeof ($.tooltip()) !== 'undefined' ||
document.write(unescape('%3Cscript src="jquery.tooltip.min.js"%3E%3C/script%3E'))</script>

I answered a similar questions at jquery ui - how to use google CDN
You can make the call using
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.9/themes/base/jquery-ui.css" type="text/css" media="all" />
<script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.5.min.js" type="text/javascript"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.9/jquery-ui.min.js" type="text/javascript"></script>
You can also link to other Ui themes by changes the name of the theme. In This case change the name base to any other theme name /base/jquery-ui.css to any other theme.
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.9/themes/base/jquery-ui.css" type="text/css" media="all" />
Check out the jQuery UI Blog for a link of all CDN links http://blog.jqueryui.com/
If you want to revert back to your host in case Google failed, you can do
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
<script type="text/javascript">
if (typeof jQuery == 'undefined')
{
document.write(unescape("%3Cscript src='/jquery.js' type='text/javascript'%3E%3C/script%3E"));
}
</script>

<script src="http://ajax.aspnetcdn.com/ajax/mvc/3.0/jquery.validate.unobtrusive.min.js" type="text/javascript"></script>
<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.7/jquery.validate.min.js" type="text/javascript"></script>
<script type="text/javascript">
if(typeof jQval == 'undefined')
{
document.write(unescape("%3Cscript src='/Scripts/jquery.validate.unobtrusive.min.js' type='text/javascript'%3E%3C/script%3E"));
document.write(unescape("%3Cscript src='/Scripts/jquery.validate.min.js' type='text/javascript'%3E%3C/script%3E"));
}
</script>
Taken from this article

Best to do all this script loading with your own Javascript code.
First try to load the CDN file by inserting a new SCRIPT element into the DOM. Then check that it has loaded by looking for an object that it defines. If the object does not appear, then insert another SCRIPT element to load the local copy. Probably best to clean up the DOM and remove SCRIPTs which failed to load as well.
Don't forget to account for timing issues, i.e. load is not instant.

Related

How to load multiple files from CDNs asynchronously (but execute them synchronously)?

When downloading multiple commonly used javascript/css files (e.g. boostrap and jquery), many topics like this one recommend the use of a CDN, with one of the main arguments that it can then be used to load them asynchronously.
How does that work? To the best of my knowledge, <script> tags in the header are read synchronously, so it won't actually look at the second CDN file until the first one is finished.
<script src="//ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
How can I make the page download the scripts asynchronously, but execute them synchronously? Or is that actually happening by default somehow? And what about CSS files, will my
<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
behave any different in that sense? I would like to understand the loading process properly before adding my own failovers to local code (for if the CDN is down), as to prevent getting stuck with synchronous downloading.
(Note that, despite the near-identical title, this is not a duplicate of this question, which is about loading scripts dynamically.)
Also note that I can't use defer (at least in the vanilla way that I know) as that would prevent me from adding said failover when the CDN is down, e.g.
<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.2.1/js/bootstrap.min.js"></script>
<script> $.fn.modal || document.write('<script src="Script/bootstrap.min.js">\x3C/script>')</script>
would be broken by simply adding defer.
It's more about parallelism than asynchronousness. (They're certainly related, but the CDN argument related to limits on multiple downloads from the same origin is about parallelism.)
How can I make the page download the scripts asynchronously, but execute them synchronously?
Any decent browser, when given the three script tags you've shown, will download them in parallel (up to its parallel-from-the-same-site limit) and then execute them in order. You don't have to do anything to make that happen. Browsers read ahead in the HTML to find resources to fetch.
Adding fallback scripts with document.write might complicate the browser's ability to do that, or even prevent it, but you can ensure it declaratively using <link rel="preload" as="script" href="..."> (more on MDN). Combining that with fallback scripts for failed CDN resources, it might look something like this:
<head>
<!-- ... -->
<link rel="preload" as="script" href="//ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js">
<link rel="preload" as="script" href="//cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js">
<link rel="preload" as="script" href="//maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js">
</head>
<body>
<!-- ... -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>if (!/*loaded condition*/) document.write(/*fallback*/);</script>
<script src="//cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script>if (!/*loaded condition*/) document.write(/*fallback*/);</script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
<script>if (!/*loaded condition*/) document.write(/*fallback*/);</script>
</body>
</html>
Note that that doesn't preload the fallbacks. You could, but then you'd be loading them even when the CDN was working, which wastes the end user's bandwidth. The fallbacks would be for the presumably-temporary degraded situation where the CDN was unavailable, where a degraded user experience is probably okay. (You could even show the user an indicator of a problem when scheduling the fallback, like Gmail's "something is taking longer than usual" indicator.)
If you're bothered by repeating the URLs and you're okay with document.write in small doses (as you seem to be), you can avoid duplicating the URLs by doing something along these lines:
<head>
<!-- ... -->
<script>
var scripts = [
{
url: "//ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js",
okay: function() { return /*check it loaded*/; }
},
{
url: "//cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js",
okay: function() { return /*check it loaded*/; }
},
{
url: "//maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js",
okay: function() { return /*check it loaded*/; }
},
];
scripts.forEach(function(script) {
document.write('<link rel="preload" as="script" href="' + script.url + '">');
});
</script>
</head>
<body>
<!-- ... -->
<script>
scripts.forEach(function(script, index) {
var fallback = script.url.substring(script.url.lastIndexOf('/') + 1);
document.write('<script src="' + script.url + '"><\/script>');
document.write('<script>if (!scripts[' + index + '].okay()) document.write(\'<script src="' + fallback + '"><\\/script>\');<\/script>');
});
</script>
</body>
</html>
(Since that's all inline script you're unlikely to transpile, I've kept the syntax to ES5 level in case you have to support obsolete environments.)
I think you can still use defer, just put your fallback code into an event handler...
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script
defer
This Boolean attribute is set to indicate to a browser that the
script is meant to be executed after the document has been parsed, but
before firing DOMContentLoaded.
Scripts with the defer attribute will prevent the DOMContentLoaded
event from firing until the script has loaded and finished evaluating.
[...]
Scripts with the defer attribute will execute in the order in which
they appear in the document.
... so DOMContentLoaded could be a good pick.
Or, you can also put the fallback code into a separate .js file, and then it can be loaded with defer too, relying on the bottom part of the quotation, so the in-order execution.

Uncaught TypeError: $(...).datepicker is not a function(anonymous function)

I found few answers on stack overflow but still cant resolve my problem.
I am running on Django but I dont think it is relevant for this error.
I try to make work my date picker java script but I am getting the error
1:27 Uncaught TypeError: $(...).datepicker is not a function(anonymous function) # 1:27fire # jquery-1.9.1.js:1037self.fireWith # jquery-1.9.1.js:1148jQuery.extend.ready # jquery-1.9.1.js:433completed # jquery-1.9.1.js:103
jquery-2.1.0.min.js:4 XHR finished loading: POST "https://localhost:26143/skypectoc/v1/pnr/parse".l.cors.a.crossDomain.send # jquery-2.1.0.min.js:4o.extend.ajax # jquery-2.1.0.min.js:4PNR.findNumbers # pnr.js:43parseContent # contentscript.js:385processMutatedElements # contentscript.js:322
This is all my scripts :
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.11.0/jquery-ui.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('.dateinput').datepicker({ format: "yyyy/mm/dd" });
});
</script>
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="../../assets/js/vendor/jquery.min.js"><\/script>')</script>
<script src="http://getbootstrap.com/dist/js/bootstrap.min.js"></script>
<!-- Just to make our placeholder images work. Don't actually copy the next line! -->
<script src="http://getbootstrap.com/assets/js/vendor/holder.min.js"></script>
<!-- IE10 viewport hack for Surface/desktop Windows 8 bug -->
<script src="http://getbootstrap.com/assets/js/ie10-viewport-bug-workaround.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$("#extra-content").hide();
$("#toggle-content").click(function(){
$("#extra-content").toggle();
});
});
</script>
any feedback will be very appreciated
What went wrong?
When you include jQuery the first time:
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.11.0/jquery-ui.js"></script>
The second script plugs itself into jQuery, and "adds" $(...).datepicker.
But then you are including jQuery once again:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
It undoes the plugging in and therefore $(...).datepicker becomes undefined.
Although the first $(document).ready block appears before that, the anonymous callback function body is not executed until all scripts are loaded, and by then $(...) (window.$ to be precise) is referring to the most recently loaded jQuery.
You would not run into this if you called $('.dateinput').datepicker immediately rather than in $(document).ready callback, but then you'd need to make sure that the target element (with class dateinput) is already in the document before the script, and it's generally advised to use the ready callback.
Solution
If you want to use datepicker from jquery-ui, it would probably make most sense to include the jquery-ui script after bootstrap. jquery-ui 1.11.4 is compatible with jquery 1.6+ so it will work fine.
Alternatively (in particular if you are not using jquery-ui for anything else), you could try bootstrap-datepicker.
The error is because you are including the script links at two places which will do the override and re-initialization of date-picker
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.11.0/jquery-ui.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('.dateinput').datepicker({ format: "yyyy/mm/dd" });
});
</script>
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
So exclude either src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"
or
src="http://code.jquery.com/ui/1.11.0/jquery-ui.js"
It will work..
if you are using ASP.NET MVC
Open the layout file "_Layout.cshtml" or your custom one
At the part of the code you see, as below:
#Scripts.Render("~/bundles/bootstrap")
#RenderSection("scripts", required: false)
#Scripts.Render("~/bundles/jquery")
Remove the line "#Scripts.Render("~/bundles/jquery")"
(at the part of the code you see) past as the latest line, as below:
#Styles.Render("~/Content/css")
#Scripts.Render("~/bundles/modernizr")
#Scripts.Render("~/bundles/jquery")
This help me and hope helps you as well.
You just need to add three file and two css links. You can either cdn's as well.
Links for the js files and css files are as such :-
jQuery.dataTables.min.js
dataTables.bootstrap.min.js
dataTables.bootstrap.min.css
bootstrap-datepicker.css
bootstrap-datepicker.js
They are valid if you are using bootstrap in your project.
I hope this will help you.
Regards,
Vivek Singla
Including more than one reference to Jquery library is the reason for the error Only Include one reference to the Jquery library and that will resolve the issue
We need to add the declaration of our jQuery plugin under interface with the same name. We don’t want to mess with the jQuery source code, so we need to create our own type definition file. I’m using React/typescript so just follow these steps
Open nodemodules and go into types folder.
Go into jQuery and open jQuery.d.ts fileand add the below code into interface JQuery<TElement = HTMLElement> extends Iterable {
daterangepicker(options?: any, callback?: Function) : any;
I’m declaring the daterangepicker function (this is the actual function that the API expose) and setting all its arguments as any ( You can go further and use specific types, but in this case, I will keep it simple ).
Now when the typescript compiler sees our interface, it will merge it with the jQuery interface and the error is gone.
That’s all!
This error is occur,because the function is not defined.
In my case i have called the datepicker function without including the datepicker js file that time I got this error.

CDN fallback issue

I was confused whether to use cdn or not , so i went through these links link1 and link2
And they told to use local scripts as a fallback from cdn
So i kept this code
<script src="https://secure.skypeassets.com/i/scom/js/skype-uri.js" async></script>
<script>
window.Skype || document.write('<script src="javascripts/skype-uri.js" async>\x3C/script>')
</script>
<!-- -->
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.9/angular.min.js"></script>
<script>
window.angular || document.write('<script src="javascripts/angular.min.js">\x3C/script>')
</script>
<!-- -->
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.9/angular-animate.min.js"></script>
<script>
window['angular-animate'] || document.write('<script src="javascripts/angular-animate.min.js">\x3C/script>')
</script>
<!-- -->
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.9/angular-aria.min.js"></script>
<script>
window['angular-aria'] || document.write('<script src="javascripts/angular-aria.min.js">\x3C/script>')
</script>
<!-- -->
<script src="https://ajax.googleapis.com/ajax/libs/angular_material/1.0.4/angular-material.min.js"></script>
<script>
window['angular-material'] || document.write('<script src="javascripts/angular-material.min.js">\x3C/script>')
</script>
The issue is it gets local files and gets same file from cdn too.
When i hit the page and monitor through charles proxy (or any other network monitoring tool)
Kinda weird but am not able to figure out the issue here.
The fallback for script using window.angular || /* fallback code*/ looks fine and should work (works for me).
Keep in mind the test doesn't refer to the script name but checks if a known global variable that should be set if the script has been loaded in fact exists. So for other scripts you need to know what global variables they set (if any) or what methods/properties they add to existing objects and check for them.
BTW the async flag on your Skype script will break this kind of test because there's a good chanse the check for Skype will execute before the browser fetches and parses the external script.
As for the stylesheet fallback this works fine (even when the local copy also fails - browsers somehow handle this problem ;)):
<link rel="stylesheet" href="//cdnurl/style.css" onerror="this.href='localcopy.css'" />
Edit: to check for angular modules you can use angular.module('moduleName') in a try-catch block (inspired by this answer):
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.9/angular-animate.min.js"></script>
<script>
try {
angular.module('ngAnimate')
} catch(e){
document.write('<script src="javascripts/angular-animate.min.js">\x3C/script>')
}
</script>

Does angularjs gets loaded on fallback of jQuery?

In the below code,
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Falback procedure</title>
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js">
</script>
<script type="text/javascript">
if(typeof jQuery === 'undefined')
document.write('<script type="text/javascript" src="../localfolder/jquery.js"></script>');
</script>
<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/angular.js/2.0.0-beta.0/angular2.js">
</script>
</head>
<body>
<p>Hello</p>
</body>
</html>
considering a scenario, where google CDN has reach-ability issues that triggers fallback mechanism of loading local jQuery library(sitting in webserver).
In such scenario, Does angularjs library get loaded? after executing document.write
You have two problems with that code that are likely to be making it not behave as you expect:
You have a literal </script> inside a script block. It doesn't matter that it's inside a string, it terminates the block it's in. You have to break it up so the browser doesn't see it as the end of the block:
<script type="text/javascript">
if(typeof jQuery === 'undefined')
document.write('<script type="text/javascript" src="../localfolder/jquery.js"><\/script>');
// Note the \------------------------------------------------------------------^
</script>
The \ there is meaningless in JavaScript, but prevents the browser from seeing </script> and thus from ending the script block prematurely. Other ways you see it done are '....<' + '/script>' or '...</scr' + 'ipt>', etc.
Your src on the Angular script is incorrect, so it won't work whether jQuery loads or not (or from where). You've made the URL relative to the path of the page, but you need to make it at least protocol-relative by adding //:
<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/angular.js/2.0.0-beta.0/angular2.js">
</script>
<!-- here --------------------------^ -->
In a comment, you asked
I was wondering, whether document.write was an asynchronous execution
No, it happens immediately when the function is run. In your case, since the function is at the top level of a script tag with no special attributes, the HTML parser has to screech to a halt and run that JavaScript code, processing any tokens the JavaScript code outputs via document.write, and waiting until the JavaScript code finishes before moving on to the Angular part.
The browser may well be able to scan ahead to preload the angular.js file, but it won't execute the contents of that file until the parser has reached that file's script tag, because the order in which scripts execute is well-defined (e.g., in document order) unless you use the async or defer attributes.

jQuery "$ is not a function" error

I swear I have included jquery in the page header, it is right there!
Nonetheless the following code, which I've included near the bottom of the page (and inline for now) gives me an error saying "TypeError: $ is not a function."
<script>
function displayResult(longA, latA, longB, latB, units) {
$("#distance").html(calcDist(longA, latA, longB, latB, units));
if (units=="m") {
$("#unitLabel").html("miles");
$("units").prop("selectedIndex",0);
} else {
$("#unitLabel").html("kilometers");
$("#units").prop("selectedIndex",1);
}
$("#longA").val(longA);
$("#latA").val(latA);
$("#longB").val(longB);
$("#latB").val(latB);
}
$("#calculateButton").click(function() { //This is the line it's complaining about
var longA=$("#longA").val();
var latA=$("#latA").val();
var longB=$("#longB").val();
var latB=$("#latB").val();
var units=$("#units").val();
displayResult(longA, latA, longB, latB, units);
})(jQuery);
</script>
Higher up in the page header I've got the following:
<script src="jquery.js" ></script>
<script src="calcDistSinglePage.js" ></script>
I'm not using Wordpress or anything, this is a very straightforward hand-coded HTML page.
Try wrapping your code in a closure (which is considered good practice anyways):
(function($) {
$("#calculateButton").click(function() {
// do stuff...
});
}(jQuery));
If this snippet still complains with the same error, there's bound to be a problem with the way you're loading the jQuery library.
Also, make sure that you don't overwrite the $ variable in your other code. For example, inside calcDistSinglePage.js.
The dollar-sign is a very straight-forward javascript variable and can be reassigned to whatever you want. According to the error, $ currently is something but not a function (otherwise you'd receive a ReferenceError stating that $ is undefined). So probably, somewhere in your code, you've overwritten it.
Make sure the jQuery library it's the first script you load.
Add this just before the closing </body> tag.
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/vendor/jquery-{{JQUERY_VERSION}}.min.js"><\/script>')</script>
Download the file locally and inside js/vendor/ add the file.
Replace the value {{JQUERY_VERSION}} in the script above adding your jquery version.
Here one CDN you could use.
https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js
https://code.jquery.com/jquery-2.1.3.min.js
You are probably linking it from a root folder that is not your HTML folder. Use an absolute path:
<script src="/jquery.js" ></script>
Or make sure jquery.js is in the same folder as your HTML.

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