Some IDL attributes are defined to reflect a particular content attribute. This means that on getting, the IDL attribute returns the current value of the content attribute, and on setting, the IDL attribute changes the value of the content attribute to the given value.
The HTMLFormControlsCollection and HTMLOptionsCollection interfaces
are collections derived from the
HTMLCollection interface. The HTMLAllCollection interface is a collection, but is not so derived.
HTMLAllCollection interfaceThe HTMLAllCollection interface is used for the legacy document.all attribute. It operates similarly to
HTMLCollection; the main differences are that it allows a staggering variety of
different (ab)uses of its methods to all end up returning something, and that it can be called as
a function as an alternative to property access.
All HTMLAllCollection objects are rooted at a Document
and have a filter that matches all elements, so the elements represented by the
collection of an HTMLAllCollection object consist of all the descendant
elements of the root Document.
Objects that implement the HTMLAllCollection interface have several unusual
behaviors, due of the fact that they have an [[IsHTMLDDA]] internal slot:
The ToBoolean abstract operation in JavaScript returns
false when given objects implementing the HTMLAllCollection interface.
The Abstract Equality Comparison algorithm,
when given objects implementing the HTMLAllCollection interface, returns true when
compared to the undefined and null values.
(Comparisons using the Strict Equality Comparison
algorithm, and Abstract Equality comparisons to other values such as strings or objects, are
unaffected.)
The typeof operator in JavaScript returns the string
"undefined" when applied to objects implementing the
HTMLAllCollection interface.
These special behaviors are motivated by a desire for compatibility with two classes of legacy
content: one that uses the presence of document.all as a
way to detect legacy user agents, and one that only supports those legacy user agents and uses
the document.all object without testing for its presence
first. [JAVASCRIPT]
lengthReturns the number of elements in the collection.
item(index)Returns the item with index index from the collection (determined by tree order).
item(name)item(name)namedItem(name)namedItem(name)Returns 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.
HTMLFormControlsCollection interfaceThe HTMLFormControlsCollection interface is used for
collections of listed
elements in form elements.
lengthReturns the number of elements in the collection.
item(index)Returns the item with index index from the collection. The items are sorted in tree order.
namedItem(name)HTMLFormControlsCollection/namedItem
Support in all current engines.
namedItem(name)Returns the item with ID or name name from the collection.
If there are multiple matching items, then a RadioNodeList object containing all those elements is returned.
Returns the value of the first checked radio button represented by the object.
Can be set, to check the first radio button with the given value represented by the object.
HTMLOptionsCollection interfaceSupport in all current engines.
The HTMLOptionsCollection interface is used for collections of option elements. It is always
rooted on a select element and has attributes and methods that manipulate that
element's descendants.
length [ = value ]Returns the number of elements in the collection.
When set to a smaller number, truncates the number of option elements in the corresponding container.
When set to a greater number, adds new blank option elements to that container.
item(index)Returns the item with index index from the collection. The items are sorted in tree order.
When index is a greater number than the number of items in the collection, adds
new blank option elements in the corresponding container.
When set to null, removes the item at index index from the collection.
When set to an option element, adds or replaces it at index index
from the collection.
namedItem(name)Returns the item with ID or name name from the collection.
If there are multiple matching items, then the first is returned.
add(element [, before ] )Inserts element before the node given by before.
The before argument can be a number, in which case element is inserted before the item with that number, or an element from the collection, in which case element is inserted before that element.
If before is omitted, null, or a number out of range, then element will be added at the end of the list.
This method will throw a "HierarchyRequestError" DOMException if
element is an ancestor of the element into which it is to be inserted.
remove(index)Removes the item with index index from the collection.
selectedIndex [ = value ]Returns the index of the first selected item, if any, or −1 if there is no selected item.
Can be set, to change the selection.
DOMStringList interfaceSupport in all current engines.
The DOMStringList interface is a non-fashionable retro way of representing a list
of strings.
lengthReturns the number of strings in strings.
item(index)Returns the string with index index from strings.
contains(string)Returns true if strings contains string, and false otherwise.