javascript disable vertical screen

With the popularity of smartphones and tablets, more and more websites are beginning to design and develop mobile versions. On mobile devices, unlike desktop computers, users can adjust the orientation of the device at will, that is, horizontal or vertical screen, which also brings certain problems. For example, when a website is displayed in portrait mode, the displayed content may be too narrow and difficult to read and operate. When the user switches to landscape mode, the page may be out of position or unable to display due to layout problems. Therefore, some developers hope to add the function of disabling vertical screen to the web page so that the page can only be displayed in landscape mode. This is where JavaScript comes in handy.

1. What is JavaScript?

JavaScript is a scripting language mainly used to develop Internet front-end, that is, browser-side interactive design. It can be understood that HTML is the structure and content of the page, CSS is the appearance and style of the page, and JavaScript is the function and dynamic effect of the page. Through scripts written in JavaScript, the page can implement some specific responses and behaviors, such as verification forms, pop-up boxes, carousel images, etc.

2. How to disable vertical screen?

1. Use CSS styles

A simple way is to use CSS styles, which can set the width of the page to 100% of the screen height, so that it can only be completed in landscape mode The entire page is displayed vertically, but the entire page cannot be displayed in portrait orientation.

<style>
body{
    width:100vh;
    overflow-x:hidden;
}
</style>

Among them, the vh unit represents 1% of the viewport height. This solution is only suitable for absolutely positioned elements and fluid layout (Responsive Layout). However, this method does not actually prevent the device from switching to portrait mode, and users can still switch orientations by rotating the device.

2. Use media queries

Another method is to use the @media media query rule in CSS3. You can set conditions. When the device height is smaller than the device width, add a rotation style to automatically rotate the content 90 degrees so that the page is always in landscape mode. In this way, no matter how the user rotates the device, the page will always be displayed in landscape mode.

@media screen and (orientation: portrait){
    //竖屏模式下的CSS样式
    body{
        transform: rotate(90deg);
        transform-origin: right top; /*定位基点为屏幕右上角*/
        width:100vh;
        overflow-x:hidden;
        position:absolute;
        top:100%; /*将页面定位到屏幕底部*/
        left:0;
    }
}

It should be noted that this method requires all content to be rotated 90 degrees, including text, pictures, buttons, etc. Although this allows the page to be displayed in landscape mode, the appearance and experience of the page will be greatly affected, and it will also cause a lot of inconvenience during the development and maintenance process.

3. Use JavaScript

In addition to the above two methods, you can also use JavaScript to disable vertical screen. This method can automatically determine and rotate based on the orientation of the device. The code is as follows:

<script>
window.onload=function(){
    var isMobile = !!navigator.userAgent.match(/AppleWebKit.*Mobile.*/);
    if(isMobile){
        var el = document.getElementsByTagName('body')[0];
        if(window.orientation == 90 || window.orientation == -90){
            el.style.display = 'none';
            alert('请将设备调回竖屏模式');
        }
        window.addEventListener("orientationchange", function() {
            if(window.orientation == 0 || window.orientation == 180){
                el.style.display = 'none';
                alert('请将设备调为横屏模式');
            }else{
                el.style.display = 'block';
            }
        }, false);
    }
};
</script>

By judging the orientation of the device, when the device is in portrait mode, the page will be hidden, and a prompt box will pop up to prompt the user to switch back to landscape mode. The page redisplays when the device orientation is changed to landscape mode.

It should be noted that when using JavaScript to disable vertical screen, you need to consider the event of device orientation change. The orientationchange event is used here. In addition, since the userAgent (user agent) of different devices and browsers may be different, sufficient testing and adaptation are required to ensure the stability and compatibility of the code.

3. Summary

Whether you use CSS styles, media queries or JavaScript, they are essentially operations and style modifications to the page to achieve the purpose of prohibiting vertical screen. However, it should be noted that banning vertical screens is somewhat controversial in itself. Some users may feel that this restricts their right to freely rotate their devices, which may create a bad impression of the website. But in any case, we should respect the user's choice and make a page with a better user experience.

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