When building web applications, form validations play a crucial role in ensuring that user input is valid and meets certain criteria. In Javascript, promises can be used to handle form validations in an efficient and organized manner. Promises help to control the asynchronous flow of operations and handle success or failure conditions.

Why use Promises for Form Validations?

Traditionally, form validations in Javascript were handled using callbacks, which often resulted in callbacks within callbacks, making the code difficult to read and maintain. Promises provide a more structured and readable approach to handling form validations.

Promises allow us to handle the success and failure states of asynchronous operations in a more intuitive way. They simplify the code structure by separating the validation logic from the code that triggered the validation. This makes it easier to understand and maintain the form validation logic.

Example Code

Let’s take a look at an example of using promises for handling form validations in Javascript:

function validateForm(formData) {
  return new Promise((resolve, reject) => {
    // Perform form validations
    if (formData.name === '') {
      reject('Name is required');
    } else if (formData.email === '') {
      reject('Email is required');
    } else if (!validateEmail(formData.email)) {
      reject('Invalid email');
    } else {
      resolve('Form validation passed');
    }
  });
}

function submitForm(formData) {
  validateForm(formData)
    .then((message) => {
      // Form validation passed, submit the form
      console.log(message);
      // Code to submit the form
    })
    .catch((error) => {
      // Form validation failed, display error message
      console.error(error);
      // Code to handle the error
    });
}

function validateEmail(email) {
  // Logic to validate email
  // Return true if valid, false otherwise
  return true;
}

// Example usage
const formData = {
  name: 'John Doe',
  email: 'johndoe@example.com',
};

submitForm(formData);

In the above example, the validateForm function returns a promise. If the form data passes all the validations, the promise is resolved with the message “Form validation passed”. If any of the validations fail, the promise is rejected with an appropriate error message.

The submitForm function then calls the validateForm function and handles the promise using the then and catch methods. If the promise is resolved, the form submission logic is executed. If the promise is rejected, the error message is displayed.

Conclusion

Using promises for handling form validations in Javascript provides a more organized and readable approach. By separating the validation logic from the code triggering the validation, promises make the code easier to understand and maintain. Promises help to control the asynchronous flow and handle success or failure conditions in a more intuitive way.