How to Set Height Equal to Dynamic Width (CSS fluid layout) in JavaScript ?

Last Updated : 06 Jun, 2023

A key component of constructing a contemporary website in web development is developing an adaptable and dynamic layout. Setting the height of an element equal to its dynamic width, often known as a CSS fluid layout, is a common difficulty in accomplishing this. When the screen size changes and you want to keep an element's aspect ratio, like that of an image or video, you can use this technique.

While CSS offers certain options for flexible design, JavaScript is needed to set the height to the dynamic width. To ensure that the element keeps the same aspect ratio regardless of the size of the screen, JavaScript can be used to determine the dynamic width and update the element's height correspondingly.

There are a few ideas and methods you should be familiar with in order to use JavaScript to set an element's height equal to its dynamic width. The following are some of the main ideas:

CSS Fluid Layout: A CSS fluid layout is a design method that enables a website's layout to change according to the user's device's screen size. In this method, percentages rather than precise pixel values are used to set the width and height of components. In this manner, elements adjust their size according to the viewport's dimensions.
Aspect Ratio: The relationship between an element's width and height is referred to as its aspect ratio. A square, for instance, has a 1:1 aspect ratio, but a widescreen movie has a 16:9 aspect ratio. To avoid distorting the element, it's crucial to keep the aspect ratio constant when setting the height to be equal to the dynamic width.
Window Resize Event: Every time a user changes the size of the browser window, the window resize event is started. It offers a chance to keep a fluid layout by updating the sizes of the page's elements.
JavaScript Get and Set Methods: The get and set methods in JavaScript are used, respectively, to retrieve and change the value of an object property. These techniques can be used to dynamically determine and set an element's width and height values dependent on the size of the screen.
CSS Flexbox: A flexible layout technique called CSS Flexbox enables for the placement and resizing of items inside of containers. It provides a great tool for designing responsive designs and may be used in conjunction with JavaScript to set the height equal to the dynamic width.
CSS Grid: A more recent layout type called CSS Grid enables you to design intricate grid layouts with precise control over element positioning and scale. It may be used with JavaScript to set the height to the dynamic width, making it a helpful tool for creating responsive designs.

Approach:

Using CSS and JavaScript: One way to achieve a CSS-fluid layout is to use CSS and JavaScript together. In this approach, we set the height of the element as a percentage of its width in CSS, and then update the element's height dynamically using JavaScript whenever the window is resized.
Using CSS Flexbox: CSS Flexbox is another method for creating a CSS-fluid layout. With the help of this layout model, it is possible to set the height to the dynamic width and create responsive designs with strong tools.
Using CSS Grid: Another layout concept that can be utilized to create a CSS fluid layout is CSS Grid. This method offers much finer-grained control over element sizing and placement. Here's an illustration:

Example:

HTML

<!DOCTYPE html>
<html>

<head>
    <title>Set Height Equal to Dynamic Width</title>
    <style>
        /* Approach 1: Using CSS and JavaScript */
        .box {
            width: 50%;
            height: 0;
            padding-bottom: 50%;
            background-color: blue;
        }

        /* Approach 2: Using CSS Flexbox */
        .container {
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .box {
            width: 50%;
            height: auto;
            background-color: blue;
        }

        /* Approach 3: Using CSS Grid */
        .container {
            display: grid;
            justify-content: center;
            align-items: center;
            grid-template-columns: 1fr;
            grid-template-rows: 1fr;
        }

        .box {
            width: 50%;
            height: auto;
            background-color: blue;
        }
    </style>
</head>

<body>
    <!-- Approach 1: Using CSS and JavaScript -->
    <div class="box"></div>
    
    <!-- Approach 2: Using CSS Flexbox -->
    <div class="container">
        <div class="box"></div>
    </div>

    <!-- Approach 3: Using CSS Grid -->
    <div class="container">
        <div class="box"></div>
    </div>

    <script>
        window.addEventListener("resize", () => {
            const box = document.querySelector(".box");
            const width = box.clientWidth;
            box.style.height = `${width}px`;
        });
    </script>
</body>

</html>

Output:

Conclusion: In conclusion, a good trick for making fluid layouts that adjust to changing screen widths in JavaScript is to make the height of an element equal to its dynamic width. You can use a variety of strategies, such as CSS plus JavaScript, CSS Flexbox, or CSS Grid. Pick the strategy that best meets your demands because each one has advantages and disadvantages of its own. You can develop web designs that appear fantastic on any platform, from computers to mobile phones, by employing these methods.