Javascript – Uncaught ReferenceError: $ is not defined

javascriptjqueryreferenceerror

How come this code throws an

Uncaught ReferenceError: $ is not defined

when it was OK before?

$(document).ready(function() {
    $('#tabs > ul').tabs({ fx: { opacity: 'toggle' } });
    $('#featuredvid > ul').tabs();
});

Results in tabs don't close anymore.

jQuery is referenced in the header:

<script language="JavaScript" type="text/javascript" src="<?php echo get_option('siteurl') ?>/js/sprinkle.js"></script>
<script language="JavaScript" type="text/javascript" src="<?php echo get_option('siteurl') ?>/js/jquery-1.2.6.min.js"></script>
<script language="JavaScript" type="text/javascript" src="<?php echo get_option('siteurl') ?>/js/jquery-ui-personalized-1.5.2.packed.js"></script>

Best Answer

You should put the references to the jquery scripts first.

<script language="JavaScript" type="text/javascript" src="/js/jquery-1.2.6.min.js"></script>
<script language="JavaScript" type="text/javascript" src="/js/jquery-ui-personalized-1.5.2.packed.js"></script>
<script language="JavaScript" type="text/javascript" src="/js/sprinkle.js"></script>

Related Solutions

Javascript – the !! (not not) operator in JavaScript

Converts Object to boolean. If it was falsey (e.g. 0, null, undefined, etc.), it will be false, otherwise, true.

!oObject  // inverted boolean
!!oObject // non inverted boolean so true boolean representation

So !! is not an operator, it's just the ! operator twice.

Real World Example "Test IE version":

const isIE8 = !! navigator.userAgent.match(/MSIE 8.0/);  
console.log(isIE8); // returns true or false

If you ⇒

console.log(navigator.userAgent.match(/MSIE 8.0/));  
// returns either an Array or null

But if you ⇒

console.log(!!navigator.userAgent.match(/MSIE 8.0/));  
// returns either true or false

Javascript – How to check a not-defined variable in JavaScript

In JavaScript, null is an object. There's another value for things that don't exist, undefined. The DOM returns null for almost all cases where it fails to find some structure in the document, but in JavaScript itself undefined is the value used.

Second, no, there is not a direct equivalent. If you really want to check for specifically for null, do:

if (yourvar === null) // Does not execute if yourvar is `undefined`

If you want to check if a variable exists, that can only be done with try/catch, since typeof will treat an undeclared variable and a variable declared with the value of undefined as equivalent.

But, to check if a variable is declared and is not undefined:

if (yourvar !== undefined) // Any scope

Previously, it was necessary to use the typeof operator to check for undefined safely, because it was possible to reassign undefined just like a variable. The old way looked like this:

if (typeof yourvar !== 'undefined') // Any scope

The issue of undefined being re-assignable was fixed in ECMAScript 5, which was released in 2009. You can now safely use === and !== to test for undefined without using typeof as undefined has been read-only for some time.

If you want to know if a member exists independent but don't care what its value is:

if ('membername' in object) // With inheritance
if (object.hasOwnProperty('membername')) // Without inheritance

If you want to to know whether a variable is truthy:

if (yourvar)

Source

Best Answer

Related Solutions

Javascript – the !! (not not) operator in JavaScript

Javascript – How to check a not-defined variable in JavaScript

Related Topic