Implementation of login window javascript

Implementation of login window JavaScript

In daily website login operations, users need to enter their account number and password, and then click the "Login" button to complete the login operation. This login operation requires the cooperation of the front-end page and the back-end service to complete. This article will introduce how to use JavaScript to implement a simple login window.

1. Front-end page design

We need to design the login window in html first. The simplest login window is a form, which contains two input boxes (account and password) and a submit button (login). We can use the <input> tag to define input boxes and buttons, and then use the <form></form> tag to define the form. The code is as follows:

<form>
    <label>账号</label>
    <input type="text" name="username" required />
    <label>密码</label>
    <input type="password" name="password" required />
    <button type="submit">登录</button>
</form>

This form contains two input boxes, namely username and password. At the same time, a required attribute is also specified to ensure that there must be a value in the input box. In order to make the internationalization more user-friendly and let users know what they need to input, the <label></label> label is added to prompt the user to input items.

2. JavaScript handles form submission

After the user enters their account number and password in the above form, they need to click the "Login" button to complete the submission operation. At this time we need to write JavaScript code to listen to the form submission event and process related logic. The code is as follows:

var form = document.querySelector('form');

form.addEventListener('submit', function(event) {
    event.preventDefault();

    var username = form.elements['username'].value;
    var password = form.elements['password'].value;

    if (username === 'admin' && password === 'admin') {
        alert('登录成功');
    } else {
        alert('账号或密码错误');
    }
});

obtains the DOM element of the form through the document.querySelector method, and then uses the addEventListener method to provide a callback function for the form's submission event. This callback function will be triggered when the "Login" button is clicked. The event parameter represents event-related information. Use the event.preventDefault method to prevent the default behavior, that is, the form submission operation.

Then, use the elements attribute of the form element to get the value in the input box to determine whether the account password meets the requirements. If the requirements are met, use the alert function to prompt the user to successfully log in; otherwise, prompt the user that the user account or password is incorrect.

3. Data submission

In the actual login operation, the account number and password entered by the user need to be submitted to the back-end service for verification. In JavaScript, you can use the XMLHttpRequest object to implement AJAX requests to achieve this purpose.

The code is as follows:

var form = document.querySelector('form');

form.addEventListener('submit', function(event) {
    event.preventDefault();

    var username = form.elements['username'].value;
    var password = form.elements['password'].value;

    var xhr = new XMLHttpRequest();
    xhr.open('POST', '/login');
    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xhr.onreadystatechange = function() {
        if (xhr.readyState === 4 && xhr.status === 200) {
            var response = JSON.parse(xhr.responseText);
            if (response.code === 0) {
                alert('登录成功');
            } else {
                alert(response.message);
            }
        }
    };
    xhr.send('username=' + encodeURIComponent(username) + '&password=' + encodeURIComponent(password));
});

Among them, the XMLHttpRequest object is used to send asynchronous HTTP requests. We use POST requests to send the username and password to the backend service as the request body content. The setRequestHeader method is used to set the request header; the onreadystatechange method is used to monitor changes in the request status and execute the callback function. When the request is successful and the return result is not empty, parse the result and determine whether the login is successful based on the return value.

4. Conclusion

Through the above steps, we implemented a simple login window and used JavaScript code to handle the form submission and data submission functions. This implementation process also demonstrates the basic syntax and DOM operations of JavaScript, and also introduces the basic use of AJAX requests. Although such an implementation is simple, it is the basis of actual projects. On this basis, the login function can be further expanded according to actual needs.

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