The IDL attribute is also known as a JavaScript property. MDN web docs
Unfortunately, there are no clear rules and the way IDL attributes behave in conjunction with their corresponding content attributes depends on the attribute. [5]
Content attributes /n A normative list of attributes that may be specified on the element [1]
2.1.9 Dependencies / Web IDL / The IDL fragments in this specification must be interpreted as required for conforming IDL fragments, as described in Web IDL. [2]
A normative definition of a DOM interface that such elements must implement. [3]
they are referred to as content attributes for HTML and XML attributes, and IDL attributes for those defined on IDL interfaces. HTML Living Standards
Some IDL attributes are defined to reflect a particular content attribute. [4]
