Key Features of the CSS Properties and Values API
Custom Property Registration
With the `CSS.registerProperty()` method, developers can define custom properties and specify how browsers should parse them. This ensures consistency and type safety for custom properties.
Type Checking and Syntax Validation
By defining a specific syntax for a custom property, the browser can enforce type checking. For example, you can specify that a property must be a valid `<color>` or `<length>`.
Default Values
Custom properties can be assigned a default value, ensuring consistent styling even when the property is not explicitly set in the CSS.
Inheritance Control
Developers can define whether a custom property should inherit its value from its parent element or not.
How to Use the CSS Properties and Values API
Registering a Custom Property in JavaScript
The `CSS.registerProperty()` method allows you to register custom properties programmatically.
Registering a Custom Property in CSS
You can achieve the same result using the @property at-rule in CSS
Real-World Applications
- Dynamic Theming: Custom properties registered with specific syntax and default values can simplify dynamic theming in web applications.
- Advanced Animations: With type-checked custom properties, developers can create animations that are more predictable and error-resistant.
- Consistency Across Components: By registering custom properties globally, you can enforce consistent styling rules across reusable components.
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>CSS Properties and Values API Demo</title>
<link rel="stylesheet" data-wphbdelayedstyle="style.css">
<script type="wphb-delay-type" src="cssPropertiesValues.js" defer></script>
</head>
<body>
<h1>CSS Properties and Values API Demo</h1>
<div class="element-with-custom-property"></div>
<script type="text/javascript" id="wphb-delayed-styles-js">
(function () {
const events = ["keydown", "mousemove", "wheel", "touchmove", "touchstart", "touchend"];
function wphb_load_delayed_stylesheets() {
document.querySelectorAll("link[data-wphbdelayedstyle]").forEach(function (element) {
element.setAttribute("href", element.getAttribute("data-wphbdelayedstyle"));
}),
events.forEach(function (event) {
window.removeEventListener(event, wphb_load_delayed_stylesheets, { passive: true });
});
}
events.forEach(function (event) {
window.addEventListener(event, wphb_load_delayed_stylesheets, { passive: true });
});
})();
</script></body>
</html>
CSS
@property --my-color {
syntax: '<color>';
initial-value: #333333;
inherits: false;
}
.element-with-custom-property {
width: 100px;
height: 100px;
background-color: var(--my-color);
}
JS
if ('registerProperty' in CSS) {
CSS.registerProperty({
name: '--my-color',
syntax: '<color>',
initialValue: '#c0ffee',
inherits: false
});
}
Conclusion
The CSS Properties and Values API is a game-changer for web developers. It brings type safety, default values, and inheritance controls to custom properties, empowering developers to build more robust and maintainable stylesheets. Whether you’re creating dynamic themes or experimenting with advanced animations, this API opens up new possibilities in CSS development.
