JavaScript implements web login registration-Front-end Q&A-php.cn

With the development of the Internet, more and more websites and applications require users to register and log in to use various functions. Implementing login and registration for websites and applications usually requires the use of back-end technology, but implementation is cumbersome and requires a long development cycle. At the same time, front-end developers can also use JavaScript technology to implement login and registration functions, providing users with a more convenient experience and faster development speed.

This article will introduce how to use JavaScript to implement basic website and application login and registration functions.

1. Front-end basic preparation

Before starting to implement the login and registration functions, you need to prepare some basic front-end technical foundations:

HTML language: the basis of web pages System, which determines the layout and content of elements in a web page.
CSS style: Provide support for web page beautification and determine the color, font, size and other styles of elements in the web page.
JavaScript language: Provides dynamic interactive functions for web pages and applications, and realizes login registration verification and other functions.

2. Website/application login implementation

Before implementing the login function, it is necessary to determine the information required for user login, including account number and password. Generally, we need to use the input box to obtain this information, and then verify whether the account number and password entered by the user are legal.

The following is the HTML code of a basic login page:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Login Page</title>
</head>
<body>
    <h1>Login Page</h1>
    <form>
        <label for="username">Username:</label>
        <input type="text" id="username"><br>
        <label for="password">Password:</label>
        <input type="password" id="password"><br>
        <button type="submit" id="loginBtn">Login</button>
    </form>
    <script src="login.js"></script>
</body>
</html>

Copy after login

In this HTML code, we use the <form> tag to include the user input box and login Button, <label> label is used to describe the purpose of the input box, <input> label is used to create the input box, <button> label is used to create a login button.

In this HTML code, we specify a JavaScript file named "login.js" to implement the login logic. Here is the code for this JavaScript file:

function doLogin() {
    // 获取用户输入的账号和密码
    var username = document.getElementById("username").value;
    var password = document.getElementById("password").value;

    // 进行账号和密码的验证
    if (username === "admin" && password === "123456") {
        alert("Login success!");
    } else {
        alert("Incorrect username or password!");
    }
}

// 监听登录按钮的点击事件
document.getElementById("loginBtn").addEventListener("click", doLogin);

Copy after login

In this code, we have created a function called doLogin() to handle the user login logic. First we obtain the account number and password entered by the user, and then verify this information. In this example, we use a simple username and password for authentication. When the username and password are entered correctly, the "Login success!" prompt box pops up, otherwise the "Incorrect username or password!" prompt box pops up.

Finally, we added a listening event for the login button through the addEventListener() function in the JavaScript code. When the button is clicked, doLogin() will be called. function to handle user input.

3. Website/application registration implementation

Similar to the implementation of the login function, we also need to first determine the information required for user registration, including account number, password and confirmation password. Here, we need to add a verification for the "Confirm Password" field. The following is the HTML code of a basic registration page:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Register Page</title>
</head>
<body>
    <h1>Register Page</h1>
    <form>
        <label for="username">Username:</label>
        <input type="text" id="username"><br>
        <label for="password">Password:</label>
        <input type="password" id="password"><br>
        <label for="confirmPassword">Confirm Password:</label>
        <input type="password" id="confirmPassword"><br>
        <button type="submit" id="registerBtn">Register</button>
    </form>
    <script src="register.js"></script>
</body>
</html>

Copy after login

Similarly, in this HTML code, we use the <form> tag to include the user input box and registration button, ## The #<label> label is used to describe the purpose of the input box, the <input> label is used to create the input box, the <button> label is used to create the registration button .

In this HTML code, we specify a JavaScript file named "register.js" to implement registration logic. Here is the code for this JavaScript file:

function doRegister() {
    // 获取用户输入的账号、密码和确认密码
    var username = document.getElementById("username").value;
    var password = document.getElementById("password").value;
    var confirmPassword = document.getElementById("confirmPassword").value;

    // 进行账号和密码的验证
    if (username === "") {
        alert("Username cannot be empty!");
    } else if (password === "" || confirmPassword === "") {
        alert("Password or confirm password cannot be empty!");
    } else if (password !== confirmPassword) {
        alert("Password and confirm password do not match!");
    } else {
        alert("Register success!");
    }
}

// 监听注册按钮的点击事件
document.getElementById("registerBtn").addEventListener("click", doRegister);

Copy after login

In this code, we have created a function called

doRegister() to handle the user registration logic. Similarly, we obtain the account number, password and confirmation password entered by the user and verify this information. In this example, we perform three verifications: the username cannot be empty, the password and confirmation password cannot be empty, and the password and confirmation password must be consistent. When these three conditions are met, a "Register success!" prompt box pops up.

Finally, we added a listening event for the registration button through the

addEventListener() function in the JavaScript code. When the button is clicked, it will call doRegister() function to handle user input.

4. Implement local storage of data

The above code completes the implementation of the basic login/registration function, but the input box will be cleared every time it is reloaded or data is entered incorrectly, resulting in a poor user experience. Therefore we need to store the data locally, that is, implement local storage. We use localStorage for data storage, which uses key-value pairs to store data and provides setItem, getItem and other related interfaces to complete storage work.

The following is the modified code example:

// 登录逻辑
function doLogin() {
  var username = document.getElementById("username").value;
  var password = document.getElementById("password").value;
  // 将数据存储到本地
  window.localStorage.setItem("username", username);
  window.localStorage.setItem("password", password);
  if (username === "admin" && password === "123456") {
    alert("Login success!");
  } else {
    alert("Incorrect username or password!");
  }
}

// 监听登录按钮的点击事件
document.getElementById("loginBtn").addEventListener("click", doLogin);

// 注册逻辑
function doRegister() {
  var username = document.getElementById("username").value;
  var password = document.getElementById("password").value;
  var confirmPassword = document.getElementById("confirmPassword").value;
  if (username === "") {
    alert("Username cannot be empty!");
  } else if (password === "" || confirmPassword === "") {
    alert("Password or confirm password cannot be empty!");
  } else if (password !== confirmPassword) {
    alert("Password and confirm password do not match!");
  } else {
    // 将数据存储到本地
    window.localStorage.setItem("username", username);
    window.localStorage.setItem("password", password);
    alert("Register success!");
  }
}

// 监听注册按钮的点击事件
document.getElementById("registerBtn").addEventListener("click", doRegister);

// 初始化登录页面的数据
function initLoginPage() {
  var username = window.localStorage.getItem("username");
  var password = window.localStorage.getItem("password");
  if (username && password) {
    document.getElementById("username").value = username;
    document.getElementById("password").value = password;
  }
}

// 初始化注册页面的数据
function initRegisterPage() {
  var username = window.localStorage.getItem("username");
  if (username) {
    document.getElementById("username").value = username;
  }
}

// 判断当前页面是登录页面还是注册页面
if (document.title === "Login Page") {
  initLoginPage();
} else if (document.title === "Register Page") {
  initRegisterPage();
}

Copy after login

In this code, we use localStorage to implement local storage of data. When the user successfully logs in or registers, we store the username and password in localStorage. When the page reloads, we get the username and password from localStorage and fill them in the corresponding input boxes. In this way, users can retain the last entered data after reloading the page, improving the convenience of page interaction.

Summarize

The above are the methods and steps for JavaScript to implement the login and registration functions of websites and applications. Through these code examples, we learned how to use JavaScript to implement the basic functions of websites and applications, and to implement local storage of data to improve the convenience of page interaction. Of course, these code examples only show the implementation of the most basic login/registration functions, and developers can perform more complex development work based on actual needs.

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