HTML
Living Standard — Last Updated 25 July 2025
Living Standard — Last Updated 25 July 2025
反映の構成要素は次のとおり：
反映されたターゲットは、要素またはElementInternalsオブジェクトである。これは一般的にコンテキストから明らかであり、反映されたIDL属性のインタフェイスと一般的にまったく同じである。ElementInternalsオブジェクトである場合、常にそのインタフェイスと同じである。
反映されたIDL属性は、属性インターフェイスのメンバーである。
反映されたコンテンツ属性名は文字列である。反映されたターゲットが要素である場合、名前空間がnullであるコンテンツ属性のローカル名を表す。反映されたターゲットがElementInternalsオブジェクトである場合、それは反映されたターゲットのターゲット要素の内部コンテンツ属性マップのキーを表す。
反映されたIDL属性は、反映されたターゲットの反映されたコンテンツ属性名を反映するように定義できる。通常、これは、IDL属性ゲッターがcontent属性の現行値を返し、セッターがコンテンツ属性の値を指定された値に変更することを意味する。
反映されたターゲットが要素である場合、反映されたIDL属性はさらにサポートElementInternalsを宣言できる。これは、ElementInternalsインターフェイスにも、同じ識別子をもつ反映されたIDL属性を持ち、反映されたIDL属性は同じ反映されたコンテンツ属性名を反映することを意味する。
The fooBar IDL attribute must reflect the foobar content attribute and support ElementInternals.
Reflected targets have these associated algorithms:
For a reflected target that is an element element, these are defined as follows:
Return element.
Let attribute be the result of running get an attribute by namespace and local name given null, the reflected content attribute name, and element.
If attribute is null, then return null.
Return attribute's value.
Set an attribute value given element, the reflected content attribute name, and value.
Remove an attribute by namespace and local name given null, the reflected content attribute name, and element.
For a reflected target that is an ElementInternals object elementInternals, they are defined as follows:
Return elementInternals's target element.
If elementInternals's target element's internal content attribute map[the reflected content attribute name] does not exist, then return null.
Return elementInternals's target element's internal content attribute map[the reflected content attribute name].
Set elementInternals's target element's internal content attribute map[the reflected content attribute name] to value.
Remove elementInternals's target element's internal content attribute map[the reflected content attribute name].
This results in somewhat redundant data structures for ElementInternals objects as their target element's internal content attribute map cannot be directly manipulated and as such reflection is only happening in a single direction. This approach was nevertheless chosen to make it less error-prone to define IDL attributes that are shared between reflected targets and benefit from common API semantics.
IDL attributes of type DOMString or DOMString? that reflect enumerated content attributes can be limited to only known values. Per the processing models below, those will cause the getters for such IDL attributes to only return keywords for those enumerated attributes, or the empty string or null.
If a reflected IDL attribute has the type DOMString:
The getter steps are:
Let element be the result of running this's get the element.
Let contentAttributeValue be the result of running this's get the content attribute.
Let attributeDefinition be the attribute definition of element's content attribute whose namespace is null and local name is the reflected content attribute name.
If attributeDefinition indicates it is an enumerated attribute and the reflected IDL attribute is defined to be limited to only known values:
If contentAttributeValue does not correspond to any state of attributeDefinition (e.g., it is null and there is no missing value default), or if it is in a state of attributeDefinition with no associated keyword value, then return the empty string.
Return the canonical keyword for the state of attributeDefinition that contentAttributeValue corresponds to.
If contentAttributeValue is null, then return the empty string.
Return contentAttributeValue.
The setter steps are to run this's set the content attribute with the given value.
If a reflected IDL attribute has the type DOMString?:
The getter steps are:
Let element be the result of running this's get the element.
Let contentAttributeValue be the result of running this's get the content attribute.
Let attributeDefinition be the attribute definition of element's content attribute whose namespace is null and local name is the reflected content attribute name.
If attributeDefinition indicates it is an enumerated attribute:
Assert: the reflected IDL attribute is limited to only known values.
Assert: contentAttributeValue corresponds to a state of attributeDefinition.
If contentAttributeValue corresponds to a state of attributeDefinition with no associated keyword value, then return null.
Return the canonical keyword for the state of attributeDefinition that contentAttributeValue corresponds to.
Return contentAttributeValue.
The setter steps are:
If the given value is null, then run this's delete the content attribute.
Otherwise, run this's set the content attribute with the given value.
If a reflected IDL attribute has the type USVString:
The getter steps are:
Let element be the result of running this's get the element.
Let contentAttributeValue be the result of running this's get the content attribute.
Let attributeDefinition be the attribute definition of element's content attribute whose namespace is null and local name is the reflected content attribute name.
If attributeDefinition indicates it contains a URL:
If contentAttributeValue is null, then return the empty string.
Let urlString be the result of encoding-parsing-and-serializing a URL given contentAttributeValue, relative to element's node document.
If urlString is not failure, then return urlString.
Return contentAttributeValue, converted to a scalar value string.
The setter steps are to run this's set the content attribute with the given value.
If a reflected IDL attribute has the type boolean:
The getter steps are:
Let contentAttributeValue be the result of running this's get the content attribute.
If contentAttributeValue is null, then return false.
Return true.
The setter steps are:
If the given value is false, then run this's delete the content attribute.
If the given value is true, then run this's set the content attribute with the empty string.
This corresponds to the rules for boolean content attributes.
If a reflected IDL attribute has the type long, optionally limited to only non-negative numbers and optionally with a default value defaultValue:
The getter steps are:
Let contentAttributeValue be the result of running this's get the content attribute.
If contentAttributeValue is not null:
Let parsedValue be the result of integer parsing contentAttributeValue if the reflected IDL attribute is not limited to only non-negative numbers; otherwise the result of non-negative integer parsing contentAttributeValue.
If parsedValue is not an error and is within the long range, then return parsedValue.
If the reflected IDL attribute has a default value, then return defaultValue.
If the reflected IDL attribute is limited to only non-negative numbers, then return −1.
Return 0.
The setter steps are:
If the reflected IDL attribute is limited to only non-negative numbers and the given value is negative, then throw an "IndexSizeError" DOMException.
Run this's set the content attribute with the given value converted to the shortest possible string representing the number as a valid integer.
If a reflected IDL attribute has the type unsigned long, optionally limited to only positive numbers, limited to only positive numbers with fallback, or clamped to the range [clampedMin, clampedMax], and optionally with a default value defaultValue:
The getter steps are:
Let contentAttributeValue be the result of running this's get the content attribute.
Let minimum be 0.
If the reflected IDL attribute is limited to only positive numbers or limited to only positive numbers with fallback, then set minimum to 1.
If the reflected IDL attribute is clamped to the range, then set minimum to clampedMin.
Let maximum be 2147483647 if the reflected IDL attribute is not clamped to the range; otherwise clampedMax.
If contentAttributeValue is not null:
Let parsedValue be the result of non-negative integer parsing contentAttributeValue.
If parsedValue is not an error and is in the range minimum to maximum, inclusive, then return parsedValue.
If parsedValue is not an error and the reflected IDL attribute is clamped to the range:
If parsedValue is less than minimum, then return minimum.
Return maximum.
If the reflected IDL attribute has a default value, then return defaultValue.
Return minimum.
The setter steps are:
If the reflected IDL attribute is limited to only positive numbers and the given value is 0, then throw an "IndexSizeError" DOMException.
Let minimum be 0.
If the reflected IDL attribute is limited to only positive numbers or limited to only positive numbers with fallback, then set minimum to 1.
Let newValue be minimum.
If the reflected IDL attribute has a default value, then set newValue to defaultValue.
If the given value is in the range minimum to 2147483647, inclusive, then set newValue to it.
Run this's set the content attribute with newValue converted to the shortest possible string representing the number as a valid non-negative integer.
Clamped to the range has no effect on the setter steps.
If a reflected IDL attribute has the type double, optionally limited to only positive numbers and optionally with a default value defaultValue:
The getter steps are:
Let contentAttributeValue be the result of running this's get the content attribute.
If contentAttributeValue is not null:
Let parsedValue be the result of floating-point number parsing contentAttributeValue.
If parsedValue is not an error and is greater than 0, then return parsedValue.
If parsedValue is not an error and the reflected IDL attribute is not limited to only positive numbers, then return parsedValue.
If the reflected IDL attribute has a default value, then return defaultValue.
Return 0.
The setter steps are:
If the reflected IDL attribute is limited to only positive numbers and the given value is not greater than 0, then return.
Run this's set the content attribute with the given value, converted to the best representation of the number as a floating-point number.
The values Infinity and Not-a-Number (NaN) values throw an exception on setting, as defined in Web IDL. [WEBIDL]
If a reflected IDL attribute has the type DOMTokenList, then its getter steps are to return a DOMTokenList object whose associated element is this and associated attribute's local name is the reflected content attribute name. Specification authors cannot use support ElementInternals for IDL attributes of this type.
If a reflected IDL attribute has the type T?, where T is either Element or an interface that inherits from Element, then with attr being the reflected content attribute name:
Its reflected target has an explicitly set attr-element, which is a weak reference to an element or null. 最初はnullである。
Its reflected target reflectedTarget has a get the attr-associated element algorithm, that runs these steps:
Let element be the result of running reflectedTarget's get the element.
Let contentAttributeValue be the result of running reflectedTarget's get the content attribute.
If reflectedTarget's explicitly set attr-element is not null:
If reflectedTarget's explicitly set attr-element is a descendant of any of element's shadow-including ancestors, then return reflectedTarget's explicitly set attr-element.
Return null.
Otherwise, if contentAttributeValue is not null, return the first element candidate, in tree order, that meets the following criteria:
candidate's ID is contentAttributeValue; and
candidate implements T.
If no such element exists, then return null.
Return null.
The getter steps are to return the result of running this's get the attr-associated element.
The setter steps are:
If the given value is null, then:
Set this's explicitly set attr-element to null.
Run this's delete the content attribute.
Return.
Run this's set the content attribute with the empty string.
Set this's explicitly set attr-element to a weak reference to the given value.
For element reflected targets only: the following attribute change steps, given element, localName, oldValue, value, and namespace, are used to synchronize between the content attribute and the IDL attribute:
If localName is not attr or namespace is not null, then return.
Set element's explicitly set attr-element to null.
Reflected IDL attributes of this type are strongly encouraged to have their identifier end in "Element" for consistency.
If a reflected IDL attribute has the type FrozenArray<T>?, where T is either Element or an interface that inherits from Element, then with attr being the reflected content attribute name:
Its reflected target has an explicitly set attr-elements, which is either a list of weak references to elements or null. 最初はnullである。
Its reflected target has a cached attr-associated elements, which is a list of elements. It is initially « ».
Its reflected target has a cached attr-associated elements object, which is a FrozenArray<T>?. 最初はnullである。
Its reflected target reflectedTarget has a get the attr-associated elements algorithm, which runs these steps:
Let elements be an empty list.
Let element be the result of running reflectedTarget's get the element.
If reflectedTarget's explicitly set attr-elements is not null:
For each attrElement in reflectedTarget's explicitly set attr-elements:
If attrElement is not a descendant of any of element's shadow-including ancestors, then continue.
Append attrElement to elements.
Otherwise:
Let contentAttributeValue be the result of running reflectedTarget's get the content attribute.
If contentAttributeValue is null, then return null.
Let tokens be contentAttributeValue, split on ASCII whitespace.
For each id of tokens:
Let candidate be the first element, in tree order, that meets the following criteria:
candidate's ID is id; and
candidate implements T.
If no such element exists, then continue.
Append candidate to elements.
Return elements.
The getter steps are:
Let elements be the result of running this's get the attr-associated elements.
If the contents of elements is equal to the contents of this's cached attr-associated elements, then return this's cached attr-associated elements object.
Let elementsAsFrozenArray be elements, converted to a FrozenArray<T>?.
Set this's cached attr-associated elements to elements.
Set this's cached attr-associated elements object to elementsAsFrozenArray.
Return elementsAsFrozenArray.
This extra caching layer is necessary to preserve the invariant that element.reflectedElements === element.reflectedElements.
The setter steps are:
If the given value is null:
Set this's explicitly set attr-elements to null.
Run this's delete the content attribute.
Return.
Run this's set the content attribute with the empty string.
Let elements be an empty list.
For each element in the given value:
Append a weak reference to element to elements.
Set this's explicitly set attr-elements to elements.
For element reflected targets only: the following attribute change steps, given element, localName, oldValue, value, and namespace, are used to synchronize between the content attribute and the IDL attribute:
If localName is not attr or namespace is not null, then return.
Set element's explicitly set attr-elements to null.
Reflected IDL attributes of this type are strongly encouraged to have their identifier end in "Elements" for consistency.
Reflection is primarily about improving web developer ergonomics by giving them typed access to content attributes through reflected IDL attributes. The ultimate source of truth, which the web platform builds upon, is the content attributes themselves. That is, specification authors must not use the reflected IDL attribute getter or setter steps, but instead must use the content attribute presence and value. (Or an abstraction on top, such as the state of an enumerated attribute.)
Two important exceptions to this are reflected IDL attributes whose type is one of the following:
T?, where T is either Element or an interface that inherits from Element
FrozenArray<T>?, where T is either Element or an interface that inherits from Element
For those, specification authors must use the reflected target's get the attr-associated element and get the attr-associated elements, respectively. The content attribute presence and value must not be used as they cannot be fully synchronized with the reflected IDL attribute.
A reflected target's explicitly set attr-element, explicitly set attr-elements, cached attr-associated elements, and cached attr-associated elements object are to be treated as internal implementation details and not to be built upon.
HTMLFormControlsCollectionおよびHTMLOptionsCollectionインターフェイスは、HTMLCollectionインターフェイスから派生するコレクションである。HTMLAllCollectionインターフェイスはコレクションであるが、派生ではない。
HTMLAllCollectionインターフェイスHTMLAllCollectionインターフェイスは、レガシーdocument.all属性に対して使用される。このインターフェイスは、HTMLCollectionと類似の動作をする。主な違いは、このインターフェイスが完全に最後には何かを返すことになるためにそのメソッドの驚くほどさまざまな異なる（不正）利用を可能にし、プロパティアクセスの代替としての機能として呼び出すことができることということである。
すべてのHTMLAllCollectionオブジェクトは、Documentでルート化され、すべての要素とマッチするフィルターを持つ。その結果HTMLAllCollectionオブジェクトのコレクションによって表される要素は、ルートDocumentのすべての子孫要素から成る。
Objects that implement the HTMLAllCollection interface are legacy platform objects with an additional [[Call]] internal method described in the section below. They also have an [[IsHTMLDDA]] internal slot.
HTMLAllCollectionインターフェイスを実装するオブジェクトには、[[IsHTMLDDA]]内部スロットを持つという事実のために、いくつかの独特な動作を持つ。
HTMLAllCollectionインターフェイスを実装している指定されるオブジェクトの場合、JavaScriptのToBoolean抽象演算はfalseを返す。
IsLooselyEqual操作は、HTMLAllCollectionインターフェイスを実装しているオブジェクトが指定される場合、undefinedおよびnull値と比較するときtrueを返す。（IsStrictlyEqual抽象操作と、文字列やオブジェクトなどの他の値とのIsLooselyEqual比較を使用した比較は影響を受けない）。
JavaScriptにおけるtypeof演算子は、HTMLAllCollectionインターフェイスを実装しているオブジェクトに適用する場合、文字列"undefined"を返す。
これらの特別な振る舞いは、レガシーコンテンツの2つのクラスとの互換性への要望によって動機付けられている：1つはレガシーユーザーエージェントを検出する手段としてdocument.allの存在を利用するものであり、もう1つはそれらのレガシーユーザーエージェントのみをサポートし、その存在を最初にテストすることなくdocument.allオブジェクトを利用するものである。[JAVASCRIPT]
[Exposed =Window ,
LegacyUnenumerableNamedProperties ]
interface HTMLAllCollection {
readonly attribute unsigned long length ;
getter Element (unsigned long index );
getter (HTMLCollection or Element )? namedItem (DOMString name );
(HTMLCollection or Element )? item (optional DOMString nameOrIndex );
// Note: HTMLAllCollection objects have a custom [[Call]] internal method and an [[IsHTMLDDA]] internal slot.
};The object's supported property indices are as defined for HTMLCollection objects.
The supported property names consist of the non-empty values of all the id attributes of all the elements represented by the collection, and the non-empty values of all the name attributes of all the "all"-named elements represented by the collection, in tree order, ignoring later duplicates, with the id of an element preceding its name if it contributes both, they differ from each other, and neither is the duplicate of an earlier entry.
The length getter steps are to return the number of nodes represented by the collection.
The indexed property getter must return the result of getting the "all"-indexed element from this given the passed index.
The namedItem(name) method steps are to return the result of getting the "all"-named element(s) from this given name.
The item(nameOrIndex) method steps are:
If nameOrIndex was not provided, return null.
Return the result of getting the "all"-indexed or named element(s) from this, given nameOrIndex.
The following elements are "all"-named elements: a, button, embed, form, frame, frameset, iframe, img, input, map, meta, object, select, and textarea
To get the "all"-indexed element from an HTMLAllCollection collection given an index index, return the indexth element in collection, or null if there is no such indexth element.
To get the "all"-named element(s) from an HTMLAllCollection collection given a name name, perform the following steps:
If name is the empty string, return null.
Let subCollection be an HTMLCollection object rooted at the same Document as collection, whose filter matches only elements that are either:
"all"-named elements with a name attribute equal to name, or
elements with an ID equal to name.
If there is exactly one element in subCollection, then return that element.
Otherwise, if subCollection is empty, return null.
Otherwise, return subCollection.
To get the "all"-indexed or named element(s) from an HTMLAllCollection collection given nameOrIndex:
If nameOrIndex, converted to a JavaScript String value, is an array index property name, return the result of getting the "all"-indexed element from collection given the number represented by nameOrIndex.
Return the result of getting the "all"-named element(s) from collection given nameOrIndex.
If argumentsList's size is zero, or if argumentsList[0] is undefined, return null.
Let nameOrIndex be the result of converting argumentsList[0] to a DOMString.
Let result be the result of getting the "all"-indexed or named element(s) from this HTMLAllCollection given nameOrIndex.
Return the result of converting result to an ECMAScript value.
The thisArgument is ignored, and thus code such as Function.prototype.call.call(document.all, null, "x") will still search for elements. (document.all.call does not exist, since document.all does not inherit from Function.prototype.)
HTMLFormControlsCollectionインターフェイスHTMLFormControlsCollectionインターフェイスは、form要素で記載要素のコレクションに使用される。
Support in all current engines.
Support in all current engines.
[Exposed =Window ]
interface HTMLFormControlsCollection : HTMLCollection {
// inherits length and item()
getter (RadioNodeList or Element )? namedItem (DOMString name ); // shadows inherited namedItem()
};
[Exposed =Window ]
interface RadioNodeList : NodeList {
attribute DOMString value ;
};collection.lengthcollectionの要素数を返す。
element = collection.item(index)element = collection[index]collectionのインデックスindexにあるアイテムを返す。アイテムはツリー順にソートされる。
element = collection.namedItem(name)HTMLFormControlsCollection/namedItem
Support in all current engines.
radioNodeList = collection.namedItem(name)element = collection[name]radioNodeList = collection[name]collection.からのIDまたはname nameとともにアイテムを返す。
複数のマッチするアイテムが存在する場合、それらの要素すべてを含むRadioNodeListオブジェクトが返される。
radioNodeList.valueradioNodeListで表される最初にチェックされたラジオボタンの値を返す。
radioNodeList.value = value値valueを持つradioNodeListで表される最初のラジオボタンをチェックする。
The object's supported property indices are as defined for HTMLCollection objects.
The supported property names consist of the non-empty values of all the id and name attributes of all the elements represented by the collection, in tree order, ignoring later duplicates, with the id of an element preceding its name if it contributes both, they differ from each other, and neither is the duplicate of an earlier entry.
The namedItem(name) method must act according to the following algorithm:
id attribute or a name attribute equal to name, then return that node and stop the algorithm.id attribute or a name attribute equal to name, then return null and stop the algorithm.RadioNodeList object representing a live view of the HTMLFormControlsCollection object, further filtered so that the only nodes in the RadioNodeList object are those that have either an id attribute or a name attribute equal to name. The nodes in the RadioNodeList object must be sorted in tree order.RadioNodeList object.Members of the RadioNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object.
Support in all current engines.
The value IDL attribute on the RadioNodeList object, on getting, must return the value returned by running the following steps:
Let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose checkedness is true. Otherwise, let it be null.
If element is null, return the empty string.
If element is an element with no value attribute, return the string "on".
Otherwise, return the value of element's value attribute.
On setting, the value IDL attribute must run the following steps:
If the new value is the string "on": let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose value content attribute is either absent, or present and equal to the new value, if any. If no such element exists, then instead let element be null.
Otherwise: let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose value content attribute is present and equal to the new value, if any. If no such element exists, then instead let element be null.
If element is not null, then set its checkedness to true.
HTMLOptionsCollectionインターフェイスSupport in all current engines.
HTMLOptionsCollectionインターフェイスは、option要素のコレクションに使用される。常にselect要素がルートであり、要素の子孫をコントロールする属性およびメソッドを持つ。
[Exposed =Window ]
interface HTMLOptionsCollection : HTMLCollection {
// inherits item(), namedItem()
[CEReactions ] attribute unsigned long length ; // shadows inherited length
[CEReactions ] setter undefined (unsigned long index , HTMLOptionElement ? option );
[CEReactions ] undefined add ((HTMLOptionElement or HTMLOptGroupElement ) element , optional (HTMLElement or long )? before = null );
[CEReactions ] undefined remove (long index );
attribute long selectedIndex ;
};collection.lengthcollectionの要素数を返す。
collection.length = value既存の長さよりも小さい数に設定するとき、collectionに対応するコンテナー内のoption要素の数が切り捨てられる。
既存の長さよりも大きい数に設定するとき、その数が100000以下の場合、collectionに対応するコンテナーに新しい空のoption要素を追加する。
element = collection.item(index)element = collection[index]collectionのインデックスindexにあるアイテムを返す。アイテムはツリー順にソートされる。
collection[index] = elementindexがコレクションで項目の数より大きい数である場合、対応するコンテナーで新しい空白のoption要素を追加する。
nullに設定する場合、collectionからインデックスindexで項目を削除する。
option要素に設定するとき、collectionのインデックスindexで追加または置換される。
element = collection.namedItem(name)element = collection[name]collection.からのIDまたはname nameとともにアイテムを返す。
複数のマッチするアイテムが存在する場合、最初のものが返される。
collection.add(element[, before])beforeによって与えられるノードの前の要素を挿入する。
before引数は数字でもよく、その場合elementはその数字をもつアイテムの前に挿入され、またはcollectionからの要素でもよい。その場合elementはその要素の前に挿入される。
beforeが省略された、null、または範囲外の数字の場合、elementはリストの最後に加えられるだろう。
elementに挿入された要素が親要素である場合、"HierarchyRequestError" DOMExceptionを投げる。
collection.remove(index)collectionからのインデックスindexをもつ項目を削除する。
collection.selectedIndexもしあるならば、最初に選ばれたアイテムのインデックスを、または選択したアイテムが存在しない場合−1を返す。
collection.selectedIndex = indexcollection内のインデックスindexのoption要素に選択を変更する。
The object's supported property indices are as defined for HTMLCollection objects.
The length getter steps are to return the number of nodes represented by the collection.
The length setter steps are:
Let current be the number of nodes represented by the collection.
If the given value is greater than current, then:
If the given value is less than current, then:
Let n be current − value.
Remove the last n nodes in the collection from their parent nodes.
Setting length never removes or adds any optgroup elements, and never adds new children to existing optgroup elements (though it can remove children from them).
The supported property names consist of the non-empty values of all the id and name attributes of all the elements represented by the collection, in tree order, ignoring later duplicates, with the id of an element preceding its name if it contributes both, they differ from each other, and neither is the duplicate of an earlier entry.
When the user agent is to set the value of a new indexed property or set the value of an existing indexed property for a given property index index to a new value value, it must run the following algorithm:
If value is null, invoke the steps for the remove method with index as the argument, and return.
Let length be the number of nodes represented by the collection.
Let n be index minus length.
If n is greater than zero, then append a DocumentFragment consisting of n-1 new option elements with no attributes and no child nodes to the select element on which the HTMLOptionsCollection is rooted.
If n is greater than or equal to zero, append value to the select element. Otherwise, replace the indexth element in the collection by value.
The add(element, before) method must act according to the following algorithm:
If element is an ancestor of the select element on which the HTMLOptionsCollection is rooted, then throw a "HierarchyRequestError" DOMException.
If before is an element, but that element isn't a descendant of the select element on which the HTMLOptionsCollection is rooted, then throw a "NotFoundError" DOMException.
If element and before are the same element, then return.
If before is a node, then let reference be that node. Otherwise, if before is an integer, and there is a beforeth node in the collection, let reference be that node. Otherwise, let reference be null.
If reference is not null, let parent be the parent node of reference. Otherwise, let parent be the select element on which the HTMLOptionsCollection is rooted.
Pre-insert element into parent node before reference.
The remove(index) method must act according to the following algorithm:
If the number of nodes represented by the collection is zero, return.
If index is not a number greater than or equal to 0 and less than the number of nodes represented by the collection, return.
Let element be the indexth element in the collection.
Remove element from its parent node.
The selectedIndex IDL attribute must act like the identically named attribute on the select element on which the HTMLOptionsCollection is rooted
DOMStringListインターフェイスSupport in all current engines.
DOMStringListインターフェイスは、文字列のリストを表現する非流行のレトロな方法である。
[Exposed =(Window ,Worker )]
interface DOMStringList {
readonly attribute unsigned long length ;
getter DOMString ? item (unsigned long index );
boolean contains (DOMString string );
};新しいAPIは、DOMStringListよりもむしろsequence<DOMString>または同等のものを使用しなければならない。
strings.lengthstrings内の文字列の数を返す。
strings[index]strings.item(index)stringsからインデックスindexをもつ文字列を返す。
strings.contains(string)stringsにstringが含まれる場合はtrueを返し、そうでなければfalseを返す。
Each DOMStringList object has an associated list.
The DOMStringList interface supports indexed properties. The supported property indices are the indices of this's associated list.
Support in all current engines.
The length getter steps are to return this's associated list's size.
Support in all current engines.
The item(index) method steps are to return the indexth item in this's associated list, or null if index plus one is greater than this's associated list's size.
Support in all current engines.
The contains(string) method steps are to return true if this's associated list contains string, and false otherwise.