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Knockout – Uncaught ReferenceError: Unable to process binding

By Jamie
In KnockoutJS
July 10, 2022
5 Min read
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If you’ve used Knockout.js in your project to process binding, at some point or another you’ve probably encountered the following error message Uncaught ReferenceError: Unable to process binding. The most likely cause is a typo somewhere or forgetting to change the context. E.g. you are within a foreach binding and forget to use $parent especially inside your jquery HTML template.

Table of contents:

foreach data bind: uncaught typeerror

I recently encountered this issue and could not find the typo anywhere. Like most developers in my situation I was getting really frustrated, banging my head against the world looking for answers. Luckily I was able to use this Knockout.js tutorial to narrow down and solve my problem.

Here is a complete example that creates a table and displays a list of books within the table. There is an unfortunate typo within one of the td data bindings.

Example to generate the Uncaught typeerror message

<!DOCTYPE html>
<html>
<head>
<title>Data Binding with KnockoutJS</title>
</head>
<body>
<table>
<thead>
<tr>
<th>Title</th>
<th>ISBN</th>
<th>Published</th>
</tr>
</thead>
<tbody data-bind="foreach: books">
<tr>
<td data-bind="text: title"></td>
<td data-bind="text: isbn"></td>
<td data-bind="text: formatDate(publishedDate)"></td>
</tr>
</tbody>
</table>
<script type='text/javascript' src='http://cdnjs.cloudflare.com/ajax/libs/knockout/3.1.0/knockout-min.js'></script>
<script>
function ViewModel() {
var self = this;
self.books = [
{
title: 'Rapid Application Development With CakePHP',
isbn: '1460954394',
publishedDate: '2011-02-17'
},
{
title: '20 Recipes for Programming MVC 3: Faster, Smarter Web Development',
isbn: '1449309860',
publishedDate: '2011-10-14'
},
{
title: '20 Recipes for Programming PhoneGap: Cross-Platform Mobile Development for Android and iPhone',
isbn: '1449319548',
publishedDate: '2012-04-06'
}
];
self.formatDate = function(dateToFormat) {
var months = new Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December");
var d = new Date(dateToFormat);
return months[d.getMonth()] + ' ' + d.getDate() + ', ' + d.getFullYear();
};
};
var viewModel = new ViewModel();
ko.applyBindings(viewModel);
</script>
</body>
</html>

Uncaught ReferenceError: Unable to process binding “text: function (){return title }”

Message: title is not defined

The error messages above is the result of running this example.

My first clue is the message states title is not defined meaning that it is unable to process binding which is where the error occurs inside my function. I can clearly see inside the books array contains a property called title inside my function. No typos with this js knockout code.

The trick to helping determine the typo is to temporarily remove the inside of the foreach as the return component and replace it with the following: so that js knockout throws no error around the unable to process binding.

Uncaught typeerror while process binding

The resulting JSON that is outputted is as follows:

{“books”:[{“title”:“Rapid Application Development With CakePHP”,“isbn”:“1460954394”,“publishedDate”:“2011-02-17”},{“title”:“20 Recipes for Programming MVC 3: Faster, Smarter Web Development”,“isbn”:“1449309860”,“publishedDate”:“2011-10-14”},{“title”:“20 Recipes for Programming PhoneGap: Cross-Platform Mobile Development for Android and iPhone”,“isbn”:“1449319548”,“publishedDate”:“2012-04-06”}]}

KO ReferenceError: Unable to process binding

Now I finally have my first clue in this message. My foreach binding is clearly not correct as the $data of my supposedly foreach is my entire view model. Looking back at my code, I missed a “:” after the foreach binding before binding to the books JavaScript array!

I would be curious to see if there is a way to convert this example into a KnockoutJS component to make this easier in the future.

So next time, you encounter this relatively vague error, try outputting the contents of $data to help understand what is contained within your data binding that is failing.

Knockout Context Hover

Since first writing this message around process binding renderrecaptcha I’ve discovered a fantastic Chrome Extension called: Knockout Context Hover. I did not write this function and I have no affiliation with it; however, I will endorse it as a fantastic function to help with catching the message: unable to process binding.

How do I fix uncaught ReferenceError is not defined?

Answer: Executing the jQuery library after loading The main reason for the error ‘Uncaught ReferenceError: $ cannot be specified’ is the executability of jQuery before the library files loaded in the library. Make sure the jQuery code is executed when the jQuery library files have been loaded.

What is uncaught ReferenceError in Javascript?

The variable has no reference to the file. Usually the variable must be declared or ensure its inclusion within the currently running script or in the scope.

How to solve TypeError: Unable to Process Binding renderReCaptcha in Magento 2.4.3 and Magento 2.4.3-P1?

Tell me the Solution for TypeError : Cannot handle binding renderCaptchas on a Magento 2.4.4 and Magento 2.4.3P1 site. If I upgrade to Magento 2.5.4.3 this error will be displayed on checkout. When you disable the Magento CAPTCHA in your storefront this error will appear. Let’s find a way to solve the RECAPTCHA problem in checkout pages.

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By Jamie July 10, 2022
End Your If

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