Detect System Theme Preference Change with JavaScript

How to Detect System Theme Preference Change Using JavaScript

We all know how popular dark mode UI is across the web. As more websites and applications switch to using this style of interface, they will need to figure out how to dynamically detect system theme preference changes. That’s where JavaScript comes in! JavaScript is a powerful programming language that can be used to programmatically detect a user's system theme preferences and change themes automatically. In this article, we’ll discuss how to detect system theme preference changes using JavaScript.

Detecting System Theme Preference Changes

Modern web browsers provide an API called the Window.matchMedia method that allows developers to detect when a user's display settings change from one theme to another. This API can be used to detect when the browser switches from light to dark mode or vice versa. To use this API, developers must first get the MediaQueryList object, which contains a list of all the properties related to the current display settings of the user's system. Once the MediaQueryList object is retrieved, developers can use the matches property of this object to decide if the user's settings have changed from one theme to another.

Let’s look at a simple example. The following code uses the window.matchMedia method to detect when the user's system has switched from light mode to dark mode. We first get the MediaQueryList object by using the window.matchMedia method with the “prefers-color-scheme: dark” parameter. We then check the matches property of the MediaQueryList object and call a function if it returns true, meaning the user switched from light mode to dark mode.

let mql = window.matchMedia('prefers-color-scheme: dark');

if(mql.matches) {
    // Call the function to apply the dark mode 
}

This is just a basic example of how to detect system theme preference changes using JavaScript. Developers can use this same technique to detect when a user changes from dark mode to light mode. Besides the window.matchMedia method, developers can also use media queries to detect these changes. Media queries can be used to detect when the browser environment changes, for example, when the user changes the viewport size, display type, orientation, etc.

Conclusion

In this article, we discussed how to detect system theme preference changes using JavaScript. We used the window.matchMedia method to detect when a user changes from light mode to dark mode. We also discussed how developers can use media queries to detect when the browser environment changes. With these tips, developers can create dynamic websites and applications that can adjust styles according to the user’s system preferences.