How to implement cross-domain and night mode in javascript

In recent years, with the development of the Internet, the interactivity of web applications has become more and more important, and the technical level of front-end development is also constantly improving. Among them, JavaScript, as a very popular programming language, is widely used in web front-end development. However, in practical applications, we often encounter a problem, which is the problem of JavaScript cross-domain access. This article will introduce a solution - using JavaScript to implement night mode, and through this to achieve JavaScript cross-domain.

1. What is Night Mode

Night mode is a black theme mode, which is opposite to the traditional daytime mode. With the widespread use of devices such as smartphones and computers, night mode is becoming more and more popular among users because it can help users reduce the damage to their eyes when using devices at night and save power. At the same time, night mode can also provide users with a better user experience.

2. Implementation of night mode

When implementing night mode, JavaScript and CSS are required. The specific steps are as follows:

1. Define CSS styles

Define the styles of two color themes in the CSS file. Here we define two theme styles of "day" and "night" respectively. .

/* 日间模式样式 */
body.day {
  background-color: #ffffff;
  color: #000000;
}

/* 夜间模式样式 */
body.night {
  background-color: #000000;
  color: #ffffff;
}

2. Define JavaScript code

In JavaScript, we need to monitor user operations, determine whether we need to switch themes, and apply styles to the page.

// 判断是否是夜间模式，默认为日间模式
var isNight = false;

// 切换主题函数
function toggleTheme() {
  if (isNight) {
    // 切换为日间模式
    document.body.classList.remove("night");
    document.body.classList.add("day");
    isNight = false;
  } else {
    // 切换为夜间模式
    document.body.classList.remove("day");
    document.body.classList.add("night");
    isNight = true;
  }
}

// 监听用户的操作
document.addEventListener("DOMContentLoaded", function(event) {
  // 判断页面是否已设置了主题
  var theme = localStorage.getItem("theme");
  if (theme === "night") {
    toggleTheme();
  }

  // 监听按钮点击事件
  var btn = document.getElementById("btn-toggle-theme");
  btn.addEventListener("click", function() {
    // 切换主题
    toggleTheme();
    // 保存用户的选择
    localStorage.setItem("theme", isNight ? "night" : "day");
  });
});

In the above code, we determine whether the user has set a theme by determining whether the "theme" item exists in localStorage and reading the value of the item. If a theme is set, switch to the corresponding style based on its value. For cases where no theme is set, we switch to day mode by default.

When the user clicks the button to switch the theme, we switch the style by calling the toggleTheme function and save the user's selection to localStorage.

3. Switch themes through buttons

In the above JavaScript code, we listen to the click event of the button to switch the theme. In the HTML file, we need to add a button element and give it an ID value.

<button id="btn-toggle-theme">切换主题</button>

When the user clicks the button, the JavaScript code switches the theme to another one and saves it to localStorage. When the user visits the page again, it will automatically switch to the corresponding style based on the theme value just saved.

3. Using night mode to implement JavaScript cross-domain

In actual development, we often need to access resources under different domain names, such as obtaining API data from other websites. However, due to browser origin policy restrictions, JavaScript scripts can only access resources under the same domain name, so cross-domain capabilities become very valuable.

Using night mode, we can also achieve JavaScript cross-domain access relatively easily. The specific steps are as follows:

1. Add access authorization on the target website to be cross-domain.

On the target website to be cross-domain, we need to add an access authorization HTTP response header, allowing Visits from local websites. We are using PHP language to implement it here. You can add the following code to the index.php file of the target website.

// 允许访问授权
header('Access-Control-Allow-Origin: http://localhost');

In the above code, we specify the domain name that is allowed to be accessed as "http://localhost", which can be modified according to actual needs. You can also use the wildcard "*" here to allow access to all domain names, but this has certain security risks and is not recommended for use in a production environment.

2. Write JavaScript code to achieve cross-domain access

On our local website, just write the following JavaScript code to achieve cross-domain access.

// 获取目标数据
fetch('http://example.com/api/data').then(function(response) {
  return response.json();
}).then(function(data) {
  console.log(data);
}).catch(function(error) {
  console.log('发生错误', error);
});

In the above code, we use the new fetch function of ES6 for cross-domain access. The fetch function returns a Promise object, and we can obtain cross-domain data by calling the then method. If an error occurs, an exception will be thrown, and we need to use the catch method to catch the exception and handle it.

When accessing the target website, the JavaScript code will carry the access authorization information of the local website, thus successfully achieving cross-domain access.

4. Summary

This article introduces how to use JavaScript to implement night mode and use night mode to implement JavaScript cross-domain access. Using night mode can give users a better experience, and it also solves the problem of cross-domain access and greatly broadens the application scope of JavaScript. Hope this article can be helpful to you.

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