Microdata DOM API - Web APIs
properties if the element has an itemscope attribute, returns an htmlpropertiescollection object with all the element's properties.
... otherwise, an empty htmlpropertiescollection object.
...this attribute returns an htmlpropertiescollection, which can be enumerated to go through each element that adds one or more properties to the item.
...And 4 more matches

HTMLElement - Web APIs
htmlelement.properties read only returns a htmlpropertiescollection… htmlelement.spellcheck is a boolean that controls spell-checking.