CSS Object Model (CSSOM)
The CSS Object Model (CSSOM) is a specification on its own.
The current draft can be found here: https://www.w3.org/TR/cssom-1/
Adding a background-image rule via the CSSOM
To add a background-image rule via the CSSOM, first get a reference to the rules of the first stylesheet:
Then, get a reference to the end of the stylesheet:
Finally, insert a background-image rule for the body element at the end of the stylesheet:
The browser identifies tokens from stylesheet and coverts them into nodes which are linked into a tree structure. The entire map of all the nodes with their associated styles of a page would be the CSS Object Model.
To display the webpage, a web browser takes following steps.
- The web browser examines your HTML and builds the DOM (Document Object Model).
- The web browser examines your CSS and builds the CSSOM (CSS Object Model).
- The web browser combines the DOM and the CSSOM to create a render tree. The web browser displays your webpage.