Troubleshooting this error is relatively simple if you understand what causes it. The “$” alias is at the core of the problem, and jQuery and WordPress offer several ways to circumvent it so you can run the functions you need.

In this article, we’ll explain what the “Uncaught TypeError: $ is not a function” error is and what causes it. Then, we’ll also show you how to troubleshoot it. Let’s get started!

What Is the “Uncaught TypeError: $ Is Not a Function” Error in WordPress?

The “Uncaught TypeError: $ is not a function” error is a common JavaScript error that occurs when the jQuery library is not loaded correctly or there’s a conflict with other scripts using the ‘$’ symbol.

In WordPress, this error has more to do with how the Content Management System (CMS) implements jQuery and less with loading problems.

jQuery is a popular JavaScript library. It’s widely used in WordPress themes and plugins for handling various dynamic elements, animations, and AJAX operations:

In jQuery, the “$” symbol is an alias for the jQuery object, which is the primary object you interact with when working with the library. It makes the code shorter, more readable, and easier to write.

The “Uncaught TypeError: $ is not a function” is somewhat difficult to troubleshoot because you won’t see a clear error message. Unlike other WordPress errors, this problem can be triggered by misconfigured elements on your site or even a 404 error page:

The most effective way to diagnose the problem is by taking a look at the developer console or by using WordPress debug logs.

What Are the Main Causes of the “Uncaught TypeError: $ Is Not a Function” Error?

The “Uncaught TypeError: $ is not a function” error has everything to do with jQuery. You’ll run into this problem when a function that includes the “$” symbol is executed while the website is being loaded.

Here are some potential causes behind the error:

1. The jQuery library is not properly loaded. If the jQuery library isn’t properly loaded or enqueued, the ‘$’ symbol won’t be recognized as a valid function and it will throw an error. This is typically not a problem in WordPress because the Content Management System (CMS) loads the library natively.
2. You’re using jQuery in noConflict mode. By default, WordPress runs jQuery in noConflict mode. That means it doesn’t recognize the “$” symbol as a function name. To use it, you’ll need to put a workaround in action.
3. Plugin or theme conflicts. Some plugins or themes may have improperly coded JavaScript that interferes with the proper functioning of jQuery or uses the ‘$’ symbol in a way that causes problems with other scripts.

To summarize, WordPress is not configured to recognize the “$” symbol. However, that doesn’t mean you can’t run jQuery code within the CMS. After all, the library is part of WordPress. What you’ll need to do is use a workaround to avoid problems with the “$” symbol.

How To Fix the “Uncaught TypeError: $ Is Not a Function” Error (2 Ways)

Before we get to work, it’s important to note that jQuery is already a part of WordPress. Some tutorials will instruct you to enqueue jQuery, but the library has been a part of the Content Management System (CMS) for a while.

WordPress also runs jQuery in “noConflict” mode out of the box. That means it releases the “$” symbol so that other libraries can use it. Instead of disabling “noConflict” mode, here’s how you should approach this problem.

1. Use “jQuery” Instead of “$”

If you run into problems while using the “$” symbol in functions, you can use “jQuery” instead. To give you an example, here’s what a basic jQuery function using “$” may look like:

$(function() {
  // Your code here will run once the DOM is ready
});

In this case, a quick fix would be to replace the “$” symbol with jQuery. The code would then look like this:

jQuery(function() {
  // This code will not trigger the error
});

Alternatively, you can “wrap” the code in an immediately invoked function expression that contains the jQuery symbol. The following example would not trigger the “Uncaught TypeError: $ is not a function” error because it uses the jQuery symbol as a wrapper:

jQuery(function ($) {
    // You can use $ inside the wrapper
    console.log($('.primary-menu'));
});

After making these changes to the code, you can use your browser’s developer console or the WordPress debug log to see if the error persists. If it does, you may need to map “jQuery” to another symbol to circumvent more errors.

2. Use a Custom Alias in jQuery

“$” is the default alias for the jQuery object. However, since WordPress runs jQuery in noConflict mode, you might need to map an alternative alias to avoid conflicts with other libraries.

This process is relatively simple, as you can map the alias to a new symbol with a single line of code:

vvar $j = jQuery;

That code replaces the default alias with “$j” but it can be anything else you want. Some developers prefer this approach versus having to type the full “jQuery” object, as we showed in the previous method.

If you’re not sure where to add this code, you can read our tutorial on how to add code to the header and footer in WordPress. Keep in mind that even if you register a new alias, you’ll still be able to use “jQuery” instead of that symbol.

Summary

WordPress enables you to use jQuery on your website. However, if you want to avoid errors such as “Uncaught TypeError: $ is not a function”, you’ll need to understand how the CMS implements the library. WordPress uses jQuery’s “noConflict” mode, which means it doesn’t recognize the “$” symbol.

The “Uncaught TypeError: $ is not a function” error appears when you try to use a function that calls jQuery using “$”. To circumvent this problem, you can type the full jQuery object instead or map the alias to a different symbol to avoid conflicts.

If you use Kinsta, you can enable WordPress debug mode in the MyKinsta dashboard to diagnose problems. Plus, all of our plans offer top-quality support to help you troubleshoot any issues that you may encounter. Check out our plans!

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To be able to fix these errors, you need to be able to understand the error message, as this will help you comprehend why the error was raised and how to fix it.

In this tutorial, we’ll talk about the “uncaught typeerror: cannot set property” error in JavaScript.

You’ll learn why this error occurs, the different reasons why you might encounter it, and the different methods of fixing it.

What Does “Uncaught Typeerror: Cannot set property” Mean in JavaScript?

A typeerror mainly occurs when you perform an operation involving incompatible data types. In our case, we’re dealing with the “uncaught typeerror: cannot set property” error, a JavaScript error which mainly occurs when you try to assign a property to a DOM element with a null value.

This error can be raised for different reasons like:

• Placing the script tag in the wrong position in your markup
• Spelling errors when referencing DOM elements
• Accessing an undefined or invalid DOM element

In the sections that follow, we’ll discuss the reasons above, how they can throw the “uncaught typeerror: cannot set property” error with code examples, and how to fix the error.

We’ll also talk about how you can determine if a variable is null or undefined.

Let’s get started!

How To Fix the “uncaught typeerror: cannot set property” in JavaScript

In this section, you’ll get to know the common causes of the “uncaught typeerror: cannot set property” error in JavaScript. Each subsection that follows is dedicated to one of those causes and its solution.

You’ll also get to visualize how to fix the error with some practical code examples.

Invalid Placement of script Tag

When a webpage loads, the JavaScript code written for the page loads as well. The way JavaScript recognizes the Document Object Model (DOM) is dependent on where you place the script tag in your code.

If you place the script tag within the head tag or above all the HTML elements within the body tag, then the script will be executed before the DOM is ready.

When JavaScript runs before the DOM is ready, it fails to get a full representation of the DOM — which means most of your variables linked to DOM elements will return as null.

Here’s an example of a code that would raise the “uncaught typeerror: cannot set property” error in JavaScript because of the position of the script tag:

<!DOCTYPE html>
<html>
  <head>
    <title>Uncaught Typeerror Error Tutorial</title>
    <script src="proxy.php?url=app.js"></script>
  </head>
  <body>
    <h1 id="heading"></h1>
  </body>
</html>

The code above has the script tag placed within the head tag. We also have a h1 element with an id of heading.

Next, we’ll try to assign text to the h1 element:

let heading = document.getElementById('heading');
heading.textContent = 'This is a heading';
//Uncaught TypeError: Cannot set properties of null (setting 'textContent')

Although the code above looks fine, the “uncaught typeerror: cannot set property” error was raised. This happened because the script had already loaded before the DOM, so our JavaScript had no knowledge of the DOM elements.

This error will also be raised if you place the script tag above other DOM elements:

<!DOCTYPE html>
<html>
  <head>
    <title>Uncaught Typeerror Error Tutorial</title>
  </head>
  <body>
    <script src="proxy.php?url=app.js"></script>
    <h1 id="heading"></h1>
  </body>
</html>

Now the script tag is above the DOM elements in the body tag, but it will still raise the “uncaught typeerror: cannot set property” error because the script loads before the DOM.

To fix this error, you have to put the script tag just before the closing body tag. This way, all the DOM elements will load before the script.

Here’s an example of correct placement:

<!DOCTYPE html>
<html>
  <head>
    <title>Uncaught Typeerror Error Tutorial</title>
  </head>
  <body>
    <h1 id="heading"></h1>
    <script src="proxy.php?url=app.js"></script>
  </body>
</html>

let heading = document.getElementById('heading');
heading.textContent = 'This is a heading'

When the code above is executed, the h1 element will have its textContent set to “This is a heading”. There will be no error.

Spelling Errors

Spelling errors are another source of raising the “uncaught typeerror: cannot set property” error.

When you misspell the attribute (ID or class) used to identify a DOM element in JavaScript, you make reference to a nonexistent element, which will return a null value.

Trying to assign a value to a null value will raise the “uncaught typeerror: cannot set property” error.

Here’s a code example to help you understand:

<!DOCTYPE html>
<html>
  <head>
    <title>Uncaught Typeerror Error Tutorial</title>
  </head>
  <body>
    <h1 id="heading"></h1>
    <script src="proxy.php?url=app.js"></script>
  </body>
</html>

let heading = document.getElementById('headin');
heading.textContent = 'Hello World!'
//Uncaught TypeError: Cannot set properties of null (setting 'textContent')

In the code above, we have a h1 tag with an id of heading.

In the JavaScript code, we made reference to the id but with a spelling error. Instead of “heading”, we wrote “headin” — that is, document.getElementById('headin'); instead of document.getElementById('heading');.

To avoid such errors, always make sure that your DOM elements are referenced properly, using the right attribute with matching spelling.

Accessing an Undefined DOM Element

In the last section, we saw how referencing a misspelled attribute can raise an “uncaught typeerror: cannot set property” error. The same is the case when we try to access a DOM element that doesn’t exist.

In the example below, we’ll try to access an id attribute that is yet to be defined in the markup:

<!DOCTYPE html>
<html>
  <head>
    <title>Uncaught Typeerror Error Tutorial</title>
  </head>
  <body>
    <h1></h1>
    <script src="proxy.php?url=app.js"></script>
  </body>
</html>

let heading = document.getElementById('headin');
heading.textContent = 'Hello World!'
//Uncaught TypeError: Cannot set properties of null (setting 'textContent')

As can be seen above, we’re trying to set the textContent of a DOM element that doesn’t exist. There is no element in our HTML code that has an id of “heading”, so this returns a null value.

If you go on to log the heading variable to the console, you’ll get a value of null returned.

How To Determine if a Variable Is ‘null’ or ‘undefined’

By this point, you’ve understood that assigning a value to a variable that is null or undefined will most likely raise an “uncaught typeerror: cannot set property” error.

But you can determine if a variable is null or undefined; before interacting with them. Although this does not fix the error, it gives some clarity on why a functionality isn’t working.

Before we discuss how to determine if a variable is null or undefined in JavaScript, it’s important to understand the difference between a null and an undefined value.

A variable is null when an empty or unknown value is assigned to the variable. The previous sections of this tutorial show practical examples of a null variable.

On the other hand, a variable is undefined when no value has been assigned to it:

let age;
console.log(age);
// undefined

In the code above, the age variable was declared, but no value was assigned to it. When logged to the console, undefined was returned.

Now that you know the difference between null and undefined, let’s have a look at how you can determine if a variable is either of those.

You can use the loose equality operator (==) to determine if a variable is either null or undefined. Here’s an example:

<!DOCTYPE html>
<html>
  <head>
    <title>Uncaught Typeerror Error Tutorial</title>
  </head>
  <body>
    <h1 id="headin"></h1>
    <script src="proxy.php?url=app.js"></script>
  </body>
</html>

let heading = document.getElementById('headin');
if (heading == null) {
console.log('Variable is null - cannot assign value to a null variable');
} else {
heading.textContent = 'Hello World!';
}

In the code above, we made a spelling error when referencing a DOM element in JavaScript.

Using an if statement, we checked to see if the value of the heading variable was null: if (heading == null) {...}

Since it returned a null value, “Variable is null – cannot assign value to a null variable” would be logged out in the console. If we had not gotten a null value, then the code in the else block would have been executed.

If you’re wondering why we didn’t include undefined in the if statement, this is because null == undefined in JavaScript, so the code in the if statement checks for both errors.

Summary

Error messages can be confusing in some cases, but they help developers figure out why their code isn’t working in order to fix it and avoid future occurrences.

Although nobody loves errors, they’re a good way to help you understand your favorite programming language better.

What’s more, fixing a coding error gives you more context when you encounter a similar error in a different project. The error we’ve discussed in this article isn’t only raised when working on vanilla JavaScript projects — you can also encounter it when working with JavaScript frameworks and libraries.

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The post How To Fix “Uncaught Typeerror: Cannot set property” Error in JavaScript appeared first on Kinsta®.

While some error messages are straightforward and easy to understand, some might be a bit confusing when you see them.

In this tutorial, we’ll talk about one of the most common JavaScript errors — the “uncaught typeerror: cannot read property” error.

At the end of this tutorial, you should understand what the “uncaught typeerror: cannot read property” means, the common causes, and how to fix them.

What Does “uncaught typeerror: cannot read property” Mean in JavaScript?

The “uncaught typeerror: cannot read property” error mainly occurs when you try to use or access an undefined variable. This error can be raised when you’re using vanilla JavaScript or any Javascript framework.

You can easily detect errors while coding by using various developer tools like the Chrome dev tools, and the Kinsta one-click staging tool to intercept errors, test your code, and more.

How To Fix the “uncaught typeerror: cannot read property” Error in JavaScript

In the sections that follow, we’ll highlight some of the causes of the “uncaught typeerror: cannot read property” error and how to fix them using code examples.

Accessing an Object Property With a Value of Undefined

In this section, we’ll discuss one of the possible causes of the “uncaught typeerror: cannot read property” error in JavaScript. This has to do with accessing an object property that is yet to be undefined.

Here’s an example:

let person;

In the code above, we created a variable called person. The intention is to make this variable an object with properties like name, age, hobby.

Assuming you forget to create these properties, you’ll get an error when you try to access them. That is:

let person;
console.log(person.name);
// Uncaught TypeError: Cannot read properties of undefined (reading 'name')

As can be seen above, we tried accessing the name property which doesn’t exist so we got an error saying: Uncaught TypeError: Cannot read properties of undefined (reading ‘name’).

This can happen to anyone as you may forget to create/add properties to your object.

Let’s go on and add some properties to the object to fix the error:

let person = {
  name: "John",
  age: 200,
  hobby: "coding"
}
console.log(person.name);
// John

In the code above, we’ve added the name property so when you try to access it, you’ll get the value of “John” returned.

Accessing an Element That Doesn’t Exist in an Array

Just like we saw in the last section with objects, you’d also get the “uncaught typeerror: cannot read property” error raised if you try to access an element in an array that is yet to be initialized.

Here’s an example:

let arr;
console.log(arr[0]);
// Uncaught TypeError: Cannot read properties of undefined (reading '0')

In the example above, we tried accessing the first element of an array called arr.

The array has been declared but not initialized — this means that no element has been assigned to it yet.

To fix this, we’ll add elements to the array before accessing them. That is:

let arr = [2,4,6,8]
console.log(arr[0]);
// 2

Accessing a DOM Element That Doesn’t Exist

When working with the Document Object Model (DOM) in JavaScript, you might encounter the “uncaught typeerror: cannot read property”.

This can happen for different reasons like spelling errors while referencing the DOM element, accessing an element that doesn’t exist, or accessing an element before the DOM has been loaded (we’ll talk about this in the next section).

In this section, you’ll see an example that throws the “uncaught typeerror: cannot read property” error for accessing an inexistent DOM element.

Here’s the HTML code:

<!DOCTYPE html>
<html>
  <head>
    <title>Error Tutorial</title>
  </head>
  <body>
    <h1 id="content">Hello World!</h1>
    <script src="proxy.php?url=app.js"></script>
  </body>
</html>

In the code above, we created a basic HTML document with a h1 element with an ID of “content”.

Here’s the JavaScript code:

let content = document.getElementById("constent");
console.log(content.textContent);
// Uncaught TypeError: Cannot read properties of null (reading 'textContent');

The code above raises the “uncaught typeerror: cannot read property” error even though it looks like we did everything right.

It’s pretty easy to miss what’s raising this error. It is raised because we spelt “constent” instead of “content” while referencing the ID of the h1 element.

That is, document.getElementById("constent"); instead of document.getElementById("content");.

The same error will be raised if you try to reference an ID or class name that is yet to be created in the DOM.

To fix this, you can simply check for spelling errors or make sure the element being referenced actually exists in the DOM.

Placing the Script Element Above Other DOM Elements Within the Body Tag

The position of your script element determines how your JavaScript code is executed in the browser.

If you place the script element above every other element in the body of your HTML document, the JavaScript code will run before the DOM has been loaded.

This means that JavaScript will not have any reference to the DOM elements because it didn’t wait for them to be loaded before executing.

Here’s an example:

<!DOCTYPE html>
<html>
  <head>
    <title>Error Tutorial</title>
  </head>
  <body>
    <script src="proxy.php?url=app.js"></script>
    <h1 id="content">Hello World!</h1>
  </body>
</html>

In the code above, we placed the script element above the h1 element.

Here’s the JavaScript code where we try to make reference to the h1 element by using its ID:

let content = document.getElementById("content");
console.log(content.textContent);
// Uncaught TypeError: Cannot read properties of null (reading 'textContent');

As expected, the “uncaught typeerror: cannot read property” error was thrown at us because JavaScript code before the h1 element could be registered to the DOM.

To fix this problem, always put your script element before the closing body tag; that is, below every other DOM element in the body of the document. This way, the script will start running after every element in the DOM has been loaded.

<!DOCTYPE html>
<html>
  <head>
    <title>Error Tutorial</title>
  </head>
  <body>
    <h1 id="content">Hello World!</h1>
    <script src="proxy.php?url=app.js"></script>
  </body>
</html>

Summary

Errors are an unavoidable part of being a developer. While they might make you frustrated while coding, they can also help learn more and master whatever programming language you’re using.

When faced with an error, you should always try to understand the error message because it will help you know where to start and what to fix. You’ll also be able to fix other errors with similar error messages.

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