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React Formik How To Use Custom Onchange And Onblur

React Formik is a popular library for managing forms in React applications. In this article, we will explore how to utilize custom onChange and onBlur handlers with Formik to enhance your form handling capabilities.

When working with forms, user interactions like typing in input fields or moving focus away from them are crucial events that often trigger form validations or other actions. Formik simplifies this process by providing built-in onChange and onBlur handlers. However, there are scenarios where you may need custom handling for these events.

To implement custom onChange and onBlur handlers with Formik, you can define your functions and pass them to the respective props of your form components. Let's delve into the practical steps involved:

1. Implementing Custom onChange Handler:
To create a custom onChange handler, you can define a function that takes the target value and updates the form state accordingly. For example, if you want to convert the input value to uppercase before setting it in the form state, you can write a function like this:

Jsx

const handleCustomChange = (e) => {
  const { name, value } = e.target;
  const uppercaseValue = value.toUpperCase();
  setFieldValue(name, uppercaseValue);
};

Here, `handleCustomChange` is a custom onChange handler that converts the input value to uppercase before updating the form state using `setFieldValue`.

2. Implementing Custom onBlur Handler:
Similarly, you can define a custom onBlur handler that performs specific actions when the input field loses focus. For example, if you want to validate the input field onBlur and display an error message if the value is invalid, you can write a function like this:

Jsx

const handleCustomBlur = (e) => {
  const { name, value } = e.target;
  if (value.trim() === '') {
    setFieldError(name, 'This field is required');
  }
};

In this snippet, `handleCustomBlur` is a custom onBlur handler that checks if the input field is empty and sets an error message using `setFieldError` if it is.

3. Integrating Custom Handlers with Formik:
Once you have defined your custom onChange and onBlur handlers, you can integrate them with your Formik form components by passing them to the `onChange` and `onBlur` props, respectively:

Jsx

By associating your custom handlers with the appropriate Formik fields, you can have full control over the form behavior based on user interactions.

In conclusion, custom onChange and onBlur handlers provide a flexible way to extend the functionality of your forms in React applications using Formik. By defining and integrating these handlers effectively, you can tailor the form behavior to suit your specific requirements and create a more interactive and user-friendly form experience. So, go ahead and explore the possibilities of custom event handling with Formik in your next project!

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