It will be checking your accuracy

Nothing is more frustrating than filling out a badly designed form. How many times you have entered a password only to be taken back with red ink proclaiming “ERROR! Password needs a capital letter, two numbers, a special character”, and whatnot. What sort of requirements they are looking for? What is the purpose behind this?

Sample for a ‘form’

Firstly, #thankYouForPickingUptheBlog. It has been written to get aware about that much-needed corner in a website, “A form”. Traditionally, the term ‘form’ has referred to a printed document that contains spaces for you to fill in the information. HTML borrows the concept of a form to refer to different elements that allow you to collect information from visitors to your site.

Whether you are adding a simple search box to your website or you need to create more complicated insurance applications, your application should always perform security checks as above mentioned on any form-submitted data on the server-side as well as the client-side. However, when we concern about client-side validation, it should not be considered an exhaustive security measure because client-side validation is too easy to bypass, so malicious users can still easily send bad data through to your server. Isn’t it worth add up more about this to your knowledge? The action of checking or proving the validity or accuracy of what you entered: its Client-side form validation

This concept helps validate the contents of the form before it is submitted to the server as:

• Minimize the work the server needs
• Allows users to see if problems of type arise faster than if the validation of the server has been completed.

What is form validation?

Form validation is a “technical process where a web-form checks if the information provided by a user is correct.” When we reach any popular site with a registration form, you will notice that they provide feedback when you do not enter your data in the format they are expecting and will receive a message such as:

Username should be according to their preference

Displays an error in enterd email address format

Password should be consist minimum of8 characters and at least 1 number

Simply, the application allows the data to be sent and (usually) saved to the server database when the information is formatted correctly; the application sends the user an error message indicating what needs to be corrected and allows them to try again when the data is not formatted correctly. This is referred to as ‘form validation.’

Here when I correctly enter my name, email address and password, it works and the error messages disappear as follow:

Here the ERROR messages have disappeared and possible to submit your information

Warning: Do not trust the data of the client to the server. Any malicious person may still need to adjust the network, even though your form validates correctly and prevents malformed feedback from the client.

Why are they asking for our checks to be validated?

• We have to concern about protecting the data of the user: We have to make secure passwords toforce users to protect easier user account details.
• We need to get the right data, in the right format: If the data stored by our users is incorrect, wrong format ,or completely skipped, our applications will not work properly.
• We want to protect ourselves: Malicious users are in a position to misuse unprotected means of harming themselves

Various forms of customer-side validation

Two forms of validation of the client-server can be found on the internet, including,

• Built-in form validation: The validation features of the HTML5 form that we addressed in several places in this blog are used in the built-in form validation. Generally, this validation does not require a lot of JavaScript. Integrated form validation is more powerful than JavaScript, although JavaScript validation is not so customizable.
• JavaScript validation is coded using JavaScript. This validation is completely customizable, but you need to create it all (or use a library).

Built-in form validation

HTML5 form validation example

One of the main advantages of HTML5 form control is the ability to validate most user data without using JavaScript functionality. HTML5 Form Validation Example When all the rules defined by the attributes below are followed by the data entered in the form field, they are considered valid. If this is not the case, the invalidity is considered.

• required: specifies that an input field must be filled out before submitting the form. The required attribute works with the following input types: text, search, URL, tel, email, password, date pickers, number, checkbox, radio, and file.
• minlength and maxlength: specifies the minimum and maximum number of characters allowed in an input field.
• min and max: specify the minimum and THE maximum values for an input field. The min and max attributes work with the following input types: number, range, date, DateTime-local, month, time ,and week
• type: Specifies whether the data needs to be a number, and email address, or some other specific preset type
• pattern: specifies a regular expression that the input field’s value is checked against, when the form is submitted.

EXAMPLE

Here follow the below link to full example to showcase the usage of HTML’s built-in validation features.

HTML5 Form Validation Examples < HTML | The Art of Web

Validating forms using JavaScript

If you wish to control or deal with older browsers that cannot support the HTML-based validation of native error messages, you must use JavaScript.

JavaScript form validation exmple

The constraints Validation API

The Constraint Validation API, consisting of a series of methods and features on the following form elements, is supported by the majority of browsers:

HTMLButtonElement (represents a <button> element)

HTMLFieldSetElement (represents a <fieldset> element)

HTMLInputElement (represents an <input> element)

HTMLOutputElement (represents an <output> element)

HTMLSelectElement (represents a <select> element)

HTMLTextAreaElement (represents a <textarea> element)

Implementing a customized error message

As you’ve already seen in the HTML5 validation limit, the browser displays an error message every time a user attempts to submit an invalid form. Depending on the browser, how this message will be displayed.

These automated messages have two drawbacks:

• There is no standard way to change their look and feel with CSS.
• They depend on the browser locale, which means that you can have a page in one language but an error message displayed in another language

Changing these error messages is one of the most common uses of API restriction validation. Take a simple example of how this is done.

<form>
  <label for="mail">I would like you to provide me with an e-mail address:</label>
  <input type="email" id="mail" name="mail">
  <button>Submit</button>
</form>

And add the following JavaScript to the page:

const email = document.getElementById("mail");

email.addEventListener("input", function (event) {
  if (email.validity.typeMismatch) {
    email.setCustomValidity("I am expecting an e-mail address!");
  } else {
    email.setCustomValidity("");
  }
});

Here we store a reference to the email input, then add an event listener to it that runs the contained code each time the value inside the input is changed.

EXAMPLE

Follow the links given below to have a practice with Edureka and JavaPoint and look at the JavaScript that implements the custom error validation in various aspects

JavaScript form validation - javatpoint

Quick Recap

Client-side form validation Often JavaScript is needed if you want to configure style and error messages, but you do need to think carefully about the consumer. Always remember to help your users to correct the data they provide. To that end, be sure:
- Displays explicit error messages.
- Please be permissive regarding the input format.
- Point out precisely where the error happens, particularly in large types.