---
title: "Implementing Form Validation with Knockout.js"
description: "Implementing form validation with Knockout.js involves several steps. Here's a detailed guide to help you get started:"
author: "Ravi Vishwakarma"
published: 2024-06-27
updated: 2024-06-27
canonical: https://www.mindstick.com/blog/304440/implementing-form-validation-with-knockout-js
category: "knockcout js"
tags: ["web development", "knockout.js", "front-end development", "knockout observables"]
reading_time: 6 minutes
---
# Implementing Form Validation with Knockout.js
Implementing [form validation](https://www.mindstick.com/forum/158694/how-can-perform-form-validation-using-jquery) with Knockout.js involves several steps. Here's a detailed guide to help you get started:
#### Step 1: Setup Your Project
First, ensure you have Knockout.js included in [your project](https://www.mindstick.com/forum/156583/best-way-to-link-bootstrap-file-in-your-project). You can do this by adding the Knockout.js library to your HTML file.
```html
Form Validation demo
```
#### Step 2: Create Your ViewModel
Create a ViewModel that will handle the form data and validation logic. You can define your observables and [validation rules](https://www.mindstick.com/forum/158293/is-it-possible-to-create-custom-validation-rules-using-jquery-validation-if-so-how) in this ViewModel.
```javascript
function AppViewModel() {
var self = this;
self.firstName = ko.observable('').extend({
required: {
message: "First name is required."
}
});
self.lastName = ko.observable('').extend({
required: {
message: "Last name is required."
}
});
self.email = ko.observable('').extend({
required: {
message: "Email is required."
},
email: {
message: "Please enter a valid email address."
}
});
self.password = ko.observable('').extend({
required: {
message: "Password is required."
},
minLength: {
message: "Password must be at least 6 characters long.",
params: 6
}
});
self.confirmPassword = ko.observable('').extend({
required: {
message: "Confirm Password is required."
},
equal: {
message: "Passwords do not match.",
params: self.password
}
});
self.errors = ko.validation.group(self);
self.submitForm = function() {
if (self.errors().length === 0) {
alert('Form is valid!');
// Proceed with form submission logic
} else {
self.errors.showAllMessages();
}
};
}
ko.applyBindings(new AppViewModel());
```
#### Step 3: Setup Knockout Validation
You'll need to include the Knockout Validation library to use the validation rules. Add the following script to your HTML:
```javascript
// Initialize Knockout validation
ko.validation.init({
registerExtenders: true, // Register custom validation rules
messagesOnModified: true, // Show validation messages as soon as a field is modified
insertMessages: true, // Insert validation messages next to the input elements
parseInputAttributes: true, // Parse HTML5 input attributes for validation rules
errorClass: 'text-danger fw-semibold', // CSS class for validation error messages
messageTemplate: null // Use default message template
}, true);
```
### Step 4: Create Your HTML Form
Now, create your HTML form and bind the input fields to your ViewModel [properties](https://www.mindstick.com/articles/23331/nootropics-7-different-types-and-their-unique-properties) using the `data-bind` attribute.
```html
```
#### Step 5: Apply Knockout Bindings
Finally, [ensure your](https://www.mindstick.com/interview/34208/how-would-you-ensure-your-api-documentation-is-developer-friendly-and-easy-to-follow) ViewModel is bound to your HTML form. This should be done in your [JavaScript](https://www.mindstick.com/articles/874/how-to-create-watermark-text-for-textbox-by-using-javascript) file as shown in the ViewModel creation step above.
```javascript
// Apply bindings
ko.applyBindings(new AppViewModel());
```
#### Combine the whole code
Here's a full example combining everything:
```html
Form Validation demo