If you are using jQuery and encounter the error TypeError: someFunction is not a function, it means that you are trying to call a function that is either undefined or not a function at all. This error happens when you try to call something that is not a function, like a variable, an object, or a string. This can happen for various reasons, such as:
- You have a typo in the function name.
- You have not loaded the script file that defines the function.
- You have overwritten the function with a variable or another value.
- You have used the wrong syntax to invoke the function.
In this article, we will show you how to troubleshoot and fix this common jQuery error.
Check the function name
The first thing you should do is to check the spelling and case of the function name. JavaScript is case-sensitive, so someFunction and somefunction are not the same. Make sure you use the exact same name as the one defined in your code or in the jQuery library.
Check the script loading order
The next thing you should do is to check the order of your script tags. If you are calling a function that is defined in another script file, you need to make sure that the script file is loaded before you call the function. For example, if you are using a jQuery plugin that defines a function called someFunction, you need to load the plugin script after the jQuery library, like this:
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script src="some-plugin.js"></script>
<script>
someFunction();
</script>
If you load the plugin script before the jQuery library, or if you forget to load the plugin script at all, you will get the error TypeError: someFunction is not a function.
Check for variable conflicts
Another possible reason for this error is that you have accidentally overwritten the function with a variable or another value. For example, if you have a global variable called someFunction, and then you try to use it as a function, you will get the error:
var someFunction = "Hello";
someFunction();
To avoid this, you should use descriptive and unique names for your variables and functions, and avoid using global variables as much as possible. You can also use namespaces or modules to organize your code and prevent name collisions.
Check the syntax
The last thing you should do is to check the syntax of your function call. If you are using jQuery, you need to use either the $() or jQuery() syntax to invoke a jQuery function. For example, if you want to use the .hide() method, you need to write something like this:
$("#some-element").hide();
jQuery("#some-element").hide();
// but not
hide("#some-element");
If you use a plain function name without the $() or jQuery() prefix, you will get the error TypeError: someFunction is not a function.