Checking if jquery is loaded using Javascript

I am attempting to check if my Jquery Library is loaded onto my HTML page. I am checking to see if it works, but something is not right. Here is what I have:

<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <script type="text/javascript" src="/query-1.6.3.min.js"></script>
        <script type="text/javascript">
          $(document).ready(function(){
             if (jQuery) {  
               // jQuery is loaded  
               alert("Yeah!");
             } else {
               // jQuery is not loaded
               alert("Doesn't Work");
             }
          });
        </script>

Answers:

Answer

something is not right

Well, you are using jQuery to check for the presence of jQuery. If jQuery isn't loaded then $() won't even run at all and your callback won't execute, unless you're using another library and that library happens to share the same $() syntax.

Remove your $(document).ready() (use something like window.onload instead):

window.onload = function() {
    if (window.jQuery) {  
        // jQuery is loaded  
        alert("Yeah!");
    } else {
        // jQuery is not loaded
        alert("Doesn't Work");
    }
}
Answer

As per this link:

if (typeof jQuery == 'undefined') {
    // jQuery IS NOT loaded, do stuff here.
}


there are a few more in comments of the link as well like,

if (typeof jQuery == 'function') {...}

//or

if (typeof $== 'function') {...}

// or

if (jQuery) {
    alert("jquery is loaded");
} else {
    alert("Not loaded");
}


Hope this covers most of the good ways to get this thing done!!

Answer
if ('undefined' == typeof window.jQuery) {
    // jQuery not present
} else {
    // jQuery present
}
Answer

You can do this fast on the console-tab when inspecting your webpage.

E.g:

$ === jQuery

If it returns true it means it's loaded.

Answer

Just a small modification that might actually solve the problem:

window.onload = function() {
   if (window.jQuery) {  
       // jQuery is loaded  
       alert("Yeah!");
   } else {
    location.reload();
   }
}

Instead of $(document).Ready(function() use window.onload = function().

Answer

You can just type window.jQuery in Console . If it return a function(e,n) ... Then it is confirmed that the jquery is loaded and working successfully.

Answer

A quick way is to run a jQuery command in the developer console. On any browser hit F12 and try to access any of the element .

 $("#sideTab2").css("background-color", "yellow");

enter image description here

Answer

If jQuery is loading asynchronously, you can wait till it is defined, checking for it every period of time:

(function() {
    var a = setInterval( function() {
        if ( typeof window.jQuery === 'undefined' ) {
            return;
        }
        clearInterval( a );

        console.log( 'jQuery is loaded' ); // call your function with jQuery instead of this
    }, 500 );
})();

This method can be used for any variable, you are waiting to appear.

Answer

CAUTION: Do not use jQuery to test your jQuery

When you are using any of the code provided by other users and if you want to display the message on your window and not on the alert or console.log, Then make sure you use javascript and not jquery.

Not everyone want to use alert or console.log

alert('jquery is working');
console.log('jquery is working');

The code below will fail to display the message
Because we are using jquery inside the else (how the hell the message displays on your screen if you do not have jquery)

if ('undefined' == typeof window.jQuery) {
    $('#selector').appendTo('jquery is NOT working');
} else {
    $('#selector').appendTo('jquery is working');
}

Use JavaScript instead

if ('undefined' == typeof window.jQuery) {
    document.getElementById('selector').innerHTML = "jquery is NOT working";
} else {
    document.getElementById('selector').innerHTML = "jquery is working";
}

Tags

Recent Questions

Top Questions

Home Tags Terms of Service Privacy Policy DMCA Contact Us Javascript

©2020 All rights reserved.