Readonly
lengthReturns the number of elements in the collection.
Returns the item with index index from the collection (determined by tree order).
Optional
nameOrIndex: stringReturns the item with ID or name name from the collection.
If there are multiple matching items, then an HTMLCollection object containing all those elements is returned.
Only button, form, iframe, input, map, meta, object, select, and textarea elements can have a name for the purpose of this method; their name is given by the value of their name attribute.
MDN Reference