CSS Object Model (CSSOM)

The CSS Object Model is a set of APIs allowing the manipulation of CSS from JavaScript. It is much like the DOM, but for the CSS rather than the HTML. It allows users to read and modify CSS style dynamically.

The values of CSS are represented untyped, that is using String objects.

Reference

Several other interfaces are also extended by the CSSOM-related specifications: Document, Window, Element, HTMLElement, HTMLImageElement, Range, MouseEvent, and SVGElement.

CSS Typed Object Model

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Obsolete CSSOM interfaces

Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

Tutorials

Determining the dimensions of elements (it needs some updating as it was made in the DHTML/Ajax era).
Managing screen orientation

Specifications

Specification
CSS Object Model (CSSOM)
CSSOM View Module
CSS Fonts Module # object-model
CSS Animations # interface-dom
CSS Conditional Rules Module # apis
CSS Custom Properties for Cascading Variables Module # apis
CSS Counter Styles # apis
CSS Device Adaptation Module # cssom
CSS Painting API # paint-worklet
CSS Typed OM