Home Web Front-end Front-end Q&A Automatic login using JavaScript

Automatic login using JavaScript

May 21, 2023 am 10:41 AM

As more and more websites and applications adopt account login, you need to enter your username and password every time you log in, which is very cumbersome. In order to improve user experience, many websites and applications provide automatic login functions. This feature records a user's login information and automatically fills it in the next time the user visits. In this article, we will introduce how to use JavaScript to implement automatic login functionality.

1. Obtain the user's login information

To implement the automatic login function, you first need to obtain the user's login information. This information usually includes username and password. This information can be obtained in several ways.

1. Obtain from Cookie

After the user logs in, the website usually creates a cookie in the user's browser to record the user's login information. This information can be obtained from cookies via JavaScript.

For example, suppose our login page has two input boxes, one for entering the username and the other for entering the password. We can use the following code to get the username and password from the cookie.

var username = getCookie("username");
var password = getCookie("password");

function getCookie(name) {
  var cookieArr = document.cookie.split(";");
  for (var i = 0; i < cookieArr.length; i++) {
    var cookiePair = cookieArr[i].split("=");
    if (name == cookiePair[0].trim()) {
      return decodeURIComponent(cookiePair[1]);
    }
  }
  return null;
}
Copy after login

2. Obtain from local storage

In addition to cookies, you can also use local storage to record the user's login information. This can be achieved using localStorage or sessionStorage. Unlike cookies, local storage is not passed on every HTTP request and is therefore more secure than cookies. The username and password can be obtained from localStorage using the following code.

var username = localStorage.getItem("username");
var password = localStorage.getItem("password");
Copy after login

2. Automatically fill in user name and password

After obtaining the user's login information, the next step is to fill this information into the login form. For most websites, the login form usually consists of a username input box and a password input box. We can autofill these forms using the following code.

document.getElementById("username").value = username;
document.getElementById("password").value = password;
Copy after login

Here, we use the getElementById method to obtain the user name and password input boxes, and fill the obtained user names and passwords into these input boxes.

3. Automatically submit the login form

After automatically filling in the user name and password, the next step is to automatically submit the login form. Normally, form submission is achieved by clicking the "Login" button, but in the case of automatic login, we need to use JavaScript to simulate clicking this button.

The following is a sample code for automatically submitting a form.

document.forms[0].submit();
Copy after login

Here, we use the submit method to submit the form.

4. The complete code to realize automatic login

By integrating the above three steps, we can realize the automatic login function. Below is a complete auto-login code example.

var username = getCookie("username");
var password = getCookie("password");

function getCookie(name) {
  var cookieArr = document.cookie.split(";");
  for (var i = 0; i < cookieArr.length; i++) {
    var cookiePair = cookieArr[i].split("=");
    if (name == cookiePair[0].trim()) {
      return decodeURIComponent(cookiePair[1]);
    }
  }
  return null;
}

if (username != null && password != null) {
  document.getElementById("username").value = username;
  document.getElementById("password").value = password;
  document.forms[0].submit();
}
Copy after login

In this example, we first obtain the username and password saved in the cookie. Then, if this information is not empty, we populate it into the login form and automatically submit the form.

It should be noted that if the user checks the "Remember Password" option after logging in, the username and password will be saved in local storage. In this case, we need to use localStorage to get this information. Similarly, we can also use localStorage to save the user's login information so that they can log in automatically the next time they visit the website.

Summary

Automatic login is a very useful function that can reduce the user's workload and improve the user experience. This article introduces how to use JavaScript to implement the automatic login function, including obtaining the user's login information, automatically filling in the user name and password, automatically submitting the login form, etc. Through these techniques, we can easily implement the automatic login function and improve user efficiency.

The above is the detailed content of Automatic login using JavaScript. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

What is useEffect? How do you use it to perform side effects? What is useEffect? How do you use it to perform side effects? Mar 19, 2025 pm 03:58 PM

The article discusses useEffect in React, a hook for managing side effects like data fetching and DOM manipulation in functional components. It explains usage, common side effects, and cleanup to prevent issues like memory leaks.

What is useContext? How do you use it to share state between components? What is useContext? How do you use it to share state between components? Mar 19, 2025 pm 03:59 PM

The article explains useContext in React, which simplifies state management by avoiding prop drilling. It discusses benefits like centralized state and performance improvements through reduced re-renders.

How do you connect React components to the Redux store using connect()? How do you connect React components to the Redux store using connect()? Mar 21, 2025 pm 06:23 PM

Article discusses connecting React components to Redux store using connect(), explaining mapStateToProps, mapDispatchToProps, and performance impacts.

How do you prevent default behavior in event handlers? How do you prevent default behavior in event handlers? Mar 19, 2025 pm 04:10 PM

Article discusses preventing default behavior in event handlers using preventDefault() method, its benefits like enhanced user experience, and potential issues like accessibility concerns.

What are the advantages and disadvantages of controlled and uncontrolled components? What are the advantages and disadvantages of controlled and uncontrolled components? Mar 19, 2025 pm 04:16 PM

The article discusses the advantages and disadvantages of controlled and uncontrolled components in React, focusing on aspects like predictability, performance, and use cases. It advises on factors to consider when choosing between them.

React's Role in HTML: Enhancing User Experience React's Role in HTML: Enhancing User Experience Apr 09, 2025 am 12:11 AM

React combines JSX and HTML to improve user experience. 1) JSX embeds HTML to make development more intuitive. 2) The virtual DOM mechanism optimizes performance and reduces DOM operations. 3) Component-based management UI to improve maintainability. 4) State management and event processing enhance interactivity.

What are the limitations of Vue 2's reactivity system with regard to array and object changes? What are the limitations of Vue 2's reactivity system with regard to array and object changes? Mar 25, 2025 pm 02:07 PM

Vue 2's reactivity system struggles with direct array index setting, length modification, and object property addition/deletion. Developers can use Vue's mutation methods and Vue.set() to ensure reactivity.

How do you define routes using the <Route> component? How do you define routes using the <Route> component? Mar 21, 2025 am 11:47 AM

The article discusses defining routes in React Router using the &lt;Route&gt; component, covering props like path, component, render, children, exact, and nested routing.

See all articles