Use jquery to implement email verification

In today's digital and networked era, email has become an indispensable part of our daily lives. Therefore, implementing email validation (Email Validation) has become a necessary skill for developers writing web applications. In this article, we will introduce how to implement email verification using jQuery.

1. Prerequisite knowledge

Before we start discussing how to use jQuery to implement email verification, we need to know some common rules for email addresses. An email address has two main parts: the username and the domain name, separated by the "@" symbol. The username can contain letters, numbers, dots (.) and underscores (_), and can start with letters or numbers, but cannot start with a dot or underscore. The domain name must contain a period, and the last part must be a two- to six-letter alphanumeric code (such as .com or .cn).

2. Requirements Analysis

Before we start writing code, we need to clarify our needs and goals. In this case, we need to implement the following aspects:

(1) When the user fills in the email address, it needs to be verified according to the above rules.

(2) Before the user attempts to submit the form, the email address needs to be verified to be valid.

(3) If the email address is invalid, an error message needs to be displayed.

3. Writing Code

Now, we can start writing code. First, we need to create an input box in the HTML code and add a class to it to identify it as the email address input box we want to verify:

<label for="email">电子邮件地址：</label>
<input type="text" name="email" id="email" class="email-input">
<span class="email-error">请输入一个有效的电子邮件地址。</span>

In the above code, we use "label" element to label the input box and associate it with the "input" element. We also added a class name "email-input" to the input box so that we can reference it later in the jQuery code. The HTML code of the error message box is as follows:

<span class="email-error">请输入一个有效的电子邮件地址。</span>

In the above code, we use the "span" element to define the error message box, and then associate it with a class name "email-error". By default, error message boxes should be hidden (display:none).

Now, we can start writing jQuery code. We divide the code into two parts: the verification function and the verification trigger function.

3.1 Validation function

We need to write a function called "validateEmail" to verify the email address. In this function, we use a regular expression to check if the email address matches the above rules:

function validateEmail(email) {
    var re = /^[w-.]+@([w-]+.)+[w-]{2,6}$/;
    return re.test(email);
}

In the above code, we use the regular expression "/^[w-.] @([w -] .) [w-]{2,6}$/" to verify the email address. The regular expression contains the following parts:

(1)^: Indicates that the string must start with the beginning part of its regular expression.

(2)[w-.]: Represents the username part of the email address. Contains letters, numbers, periods, and underscores. Since the dot has a special meaning in regular expressions, it needs to be escaped by preceding it with a backslash.

(3)@: Represents the separator between the username and domain name of the email address.

(4)([w-] .): Indicates the domain name part of the email address. Contains one or more consecutive combinations of letters, numbers, hyphens, and periods. Because the " " symbol is outside the brackets, at least one combination must match.

(5)[w-]{2,6}: Represents the last part of the email address (also known as the top-level domain name or TLD). It must be a combination of two to six letters or numbers. Because different countries use different TLDs, the range {2,6} is used here.

(6)$: Indicates that the string must end with the end part of its regular expression.

After passing the email address to the validateEmail function, the function will execute the regular expression and return true or false to indicate whether the address is valid.

3.2 Validation Trigger Function

Now, we need to write a function called "validateEmailField" to validate the email address and show or hide the error message box if needed:

function validateEmailField() {
    var emailInput = $('#email');
    var emailError = $('.email-error');
    if (validateEmail(emailInput.val())) {
        emailError.hide();
    } else {
        emailError.show();
    }
}

In the above code, we first use jQuery selector to get the input box and error message box. We then call the "validateEmail" function to check if the email address is valid. If the email address is valid, the error message box is hidden. Otherwise, display this message box.

Now, we also need to add a listener on the input box to automatically trigger validation when the user fills in their email address:

$('.email-input').on('keyup', function() {
    validateEmailField();
});

In the above code, we use jQuery listener to monitor any keys entered by the user into the input box and then call the "validateEmailField" function to validate the entered email address.

Finally, if we want to validate all input fields before the form is submitted, we can add the following code:

$('form').submit(function() {
    var emailInput = $('#email');
    var emailError = $('.email-error');
    if (!validateEmail(emailInput.val())) {
        emailError.show();
        return false;
    }
    return true;
});

In the above code, we added a listener to monitor the form submission event and then check if the email address is valid. If the email address is invalid, display an error message box and return false to prevent form submission. Otherwise, the form will be submitted.

4. Conclusion

In this article, we demonstrated how to implement email address verification using jQuery. We used regular expressions to verify the format of the email address and wrote two JavaScript functions to complete the verification process. Finally, we also demonstrated how to integrate email address validation into a web form to ensure the validity of user input. These techniques are very useful in many web applications, so we recommend that you master them to improve your web development skills.

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