JavaScript implements login verification

With the popularity of the Internet, various websites and applications have increasing demands for user login. The ensuing problem is that the security of users' accounts and personal information has become more critical. Therefore, in order to ensure the security of user accounts, login verification has become very important. This article will introduce how to use javascript to implement a simple login verification function.

1. Obtaining user input

First of all, on a website or application, the first step in login verification is to obtain the account number and password entered by the user. In the front-end page, we can use HTML form elements to achieve this. For example:

<form>
  <label>账号:</label>
  <input type="text" id="username">
  <label>密码:</label>
  <input type="password" id="password">
  <button id="submitBtn" type="button">登陆</button>
</form>

In this form, we use two input elements to obtain the account number and password entered by the user, and use a button element to trigger the login verification function.

2. Processing user input

After obtaining user input, we need to process the value entered by the user. First, we need to get the value of the account and password. You can use the getElementById method in javascript to get the elements in the page. For example:

var username = document.getElementById("username").value;
var password = document.getElementById("password").value;

Here, we obtain the element of the input box and obtain the value entered by the user through the value attribute.

Next, we can do some checks on the values ​​entered by the user. For example, check whether the input box is empty or whether the input conforms to the specified format. For example:

if(username === ""){
   alert("请输入账号！");
   return;
}

if(password === ""){
  alert("请输入密码！");
  return;
}

if(username.length < 6 || username.length > 20){
  alert("账号长度应为6-20个字符！");
  return;
}

Here, we have done some basic checks on the account and password values. If they do not meet the requirements, the corresponding prompt box will pop up and the subsequent verification steps will not be performed.

3. Verify user input

After processing the user input, we need to send the obtained account number and password to the server for verification. In a real environment, the server will verify the account number entered by the user. Match the database with the password, and if the match is successful, return information indicating successful login, otherwise return error information.

In this example, we simulate the server's verification process. We can define a function to verify the account and password values ​​entered by the user. For example:

function verify(username, password){
  if(username === "admin" && password === "123456"){
    return true;
  }else{
   return false;
  }
}

Here, we assume a fixed account number and password. If the entered account number and password meet this condition, the function returns true, otherwise it returns false.

When verifying, we need to call this function and pass the obtained account number and password as parameters. For example:

if(verify(username,password)){
  alert("登陆成功！");
}else{
  alert("账号或密码错误，请重新输入！");
}

Here, if the verification is successful, a "Login Successful" prompt box will pop up, otherwise a "Account or Password Wrong" prompt box will pop up, asking the user to re-enter.

4. Complete code

Combined with the above steps, we can completely implement a simple login verification function. The complete code is as follows:

  
  



<form>
  <label>账号:</label>
  <input type="text" id="username">
  <label>密码:</label>
  <input type="password" id="password">
  <button id="submitBtn" type="button">登陆</button>
</form>

<script>
  var submitBtn = document.getElementById("submitBtn");
  submitBtn.addEventListener("click", function(){
      var username = document.getElementById("username").value;
      var password = document.getElementById("password").value;

      if(username === ""){
         alert("请输入账号！");
         return;
      }

      if(password === ""){
        alert("请输入密码！");
        return;
      }

      if(username.length < 6 || username.length > 20){
        alert("账号长度应为6-20个字符！");
        return;
      }

      if(verify(username,password)){
        alert("登陆成功！");
      }else{
        alert("账号或密码错误，请重新输入！");
      }

  });

  function verify(username, password){
    if(username === "admin" && password === "123456"){
      return true;
    }else{
      return false;
    }
  }

</script>

Through the above code, we can understand how to use javascript to implement a simple login verification function. For real web applications, more complex algorithms and methods are needed to ensure The user's account is safe.

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