HTML

Review Draft: search element with form functionality — Last Updated 1 December 2021

1. 1. 2.6 Common DOM interfaces
      1. 2.6.1 Reflecting content attributes in IDL attributes
      2. 2.6.2 Collections
         1. 2.6.2.1 The HTMLAllCollection interface
            1. 2.6.2.1.1 [[Call]] ( thisArgument, argumentsList )
         2. 2.6.2.2 The HTMLFormControlsCollection interface
         3. 2.6.2.3 The HTMLOptionsCollection interface
      3. 2.6.3 The DOMStringList interface

2.6 Common DOM interfaces

2.6.1 Reflecting content attributes in IDL attributes

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.

In general, on getting, if the content attribute is not present, the IDL attribute must act as if the content attribute's value is the empty string; and on setting, if the content attribute is not present, it must first be added.

If a reflecting IDL attribute is a USVString attribute whose content attribute is defined to contain a URL, then on getting, if the content attribute is absent, the IDL attribute must return the empty string. Otherwise, the IDL attribute must parse the value of the content attribute relative to the element's node document and if that is successful, return the resulting URL string. If parsing fails, then the value of the content attribute must be returned instead, converted to a USVString. On setting, the content attribute must be set to the specified new value.

If a reflecting IDL attribute is a DOMString attribute whose content attribute is an enumerated attribute, and the IDL attribute is limited to only known values, then, on getting, the IDL attribute must return the keyword value associated with the state the attribute is in, if any, or the empty string if the attribute is in a state that has no associated keyword value or if the attribute is not in a defined state (e.g. the attribute is missing and there is no missing value default). If there are multiple keyword values for the state, then return the conforming one. If there are multiple conforming keyword values, then one will be designated the canonical keyword; choose that one. On setting, the content attribute must be set to the specified new value.

If a reflecting IDL attribute is a nullable DOMString attribute whose content attribute is an enumerated attribute, then, on getting, if the corresponding content attribute is in its missing value default state then the IDL attribute must return null, otherwise, the IDL attribute must return the keyword value associated with the state the attribute is in. If there are multiple keyword values for the state, then return the conforming one. If there are multiple conforming keyword values, then one will be designated the canonical keyword; choose that one. On setting, if the new value is null, the content attribute must be removed, and otherwise, the content attribute must be set to the specified new value.

If a reflecting IDL attribute is a DOMString or USVString attribute but doesn't fall into any of the above categories, then the getting and setting must be done in a transparent, case-preserving manner.

If a reflecting IDL attribute is a boolean attribute, then on getting the IDL attribute must return true if the content attribute is set, and false if it is absent. On setting, the content attribute must be removed if the IDL attribute is set to false, and must be set to the empty string if the IDL attribute is set to true. (This corresponds to the rules for boolean content attributes.)

If a reflecting IDL attribute has a signed integer type (long) then, on getting, the content attribute must be parsed according to the rules for parsing signed integers, and if that is successful, and the value is in the range of the IDL attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, then the default value must be returned instead, or 0 if there is no default value. On setting, the given value must be converted to the shortest possible string representing the number as a valid integer and then that string must be used as the new content attribute value.

If a reflecting IDL attribute has a signed integer type (long) that is limited to only non-negative numbers then, on getting, the content attribute must be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range of the IDL attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or −1 if there is no default value. On setting, if the value is negative, the user agent must throw an "IndexSizeError" DOMException. Otherwise, the given value must be converted to the shortest possible string representing the number as a valid non-negative integer and then that string must be used as the new content attribute value.

If a reflecting IDL attribute has an unsigned integer type (unsigned long) then, on getting, the content attribute must be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range 0 to 2147483647 inclusive, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 0 if there is no default value. On setting, first, if the new value is in the range 0 to 2147483647, then let n be the new value, otherwise let n be the default value, or 0 if there is no default value; then, n must be converted to the shortest possible string representing the number as a valid non-negative integer and that string must be used as the new content attribute value.

If a reflecting IDL attribute has an unsigned integer type (unsigned long) that is limited to only non-negative numbers greater than zero, then the behavior is similar to the previous case, but zero is not allowed. On getting, the content attribute must first be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range 1 to 2147483647 inclusive, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 1 if there is no default value. On setting, if the value is zero, the user agent must throw an "IndexSizeError" DOMException. Otherwise, first, if the new value is in the range 1 to 2147483647, then let n be the new value, otherwise let n be the default value, or 1 if there is no default value; then, n must be converted to the shortest possible string representing the number as a valid non-negative integer and that string must be used as the new content attribute value.

If a reflecting IDL attribute has an unsigned integer type (unsigned long) that is limited to only non-negative numbers greater than zero with fallback, then the behavior is similar to the previous case, but disallowed values are converted to the default value. On getting, the content attribute must first be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range 1 to 2147483647 inclusive, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead. On setting, first, if the new value is in the range 1 to 2147483647, then let n be the new value, otherwise let n be the default value; then, n must be converted to the shortest possible string representing the number as a valid non-negative integer and that string must be used as the new content attribute value.

If a reflecting IDL attribute has an unsigned integer type (unsigned long) that is clamped to the range [min, max], then on getting, the content attribute must first be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is between min and max inclusive, the resulting value must be returned. If it fails, the default value must be returned. If it succeeds but the value is less than min, min must be returned. If it succeeds but the value is greater than max, max must be returned. On setting, it behaves the same as setting a regular reflected unsigned integer.

If a reflecting IDL attribute has a floating-point number type (double or unrestricted double), then, on getting, the content attribute must be parsed according to the rules for parsing floating-point number values, and if that is successful, the resulting value must be returned. If, on the other hand, it fails, or if the attribute is absent, the default value must be returned instead, or 0.0 if there is no default value. On setting, the given value must be converted to the best representation of the number as a floating-point number and then that string must be used as the new content attribute value.

If a reflecting IDL attribute has a floating-point number type (double or unrestricted double) that is limited to numbers greater than zero, then the behavior is similar to the previous case, but zero and negative values are not allowed. On getting, the content attribute must be parsed according to the rules for parsing floating-point number values, and if that is successful and the value is greater than 0.0, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 0.0 if there is no default value. On setting, if the value is less than or equal to zero, then the value must be ignored. Otherwise, the given value must be converted to the best representation of the number as a floating-point number and then that string must be used as the new content attribute value.

The values Infinity and Not-a-Number (NaN) values throw an exception on setting, as defined in Web IDL. [WEBIDL]

If a reflecting IDL attribute has the type DOMTokenList, then on getting it must return a DOMTokenList object whose associated element is the element in question and whose associated attribute's local name is the name of the attribute in question.

2.6.2 Collections

The HTMLFormControlsCollection and HTMLOptionsCollection interfaces are collections derived from the HTMLCollection interface. The HTMLAllCollection interface is a collection, but is not so derived.

2.6.2.1 The HTMLAllCollection interface

The 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 are legacy platform objects with an additional [[Call]] internal method described in the section below. They also have an [[IsHTMLDDA]] internal slot.

[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:

1. If nameOrIndex was not provided, return null.

2. 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, search, select, and textarea

To get the "all"-indexed element from an HTMLAllCollection collection given an index index, return the index^th element in collection, or null if there is no such index^th element.

To get the "all"-named element(s) from an HTMLAllCollection collection given a name name, perform the following steps:

1. If name is the empty string, return null.

2. 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.

3. If there is exactly one element in subCollection, then return that element.

4. Otherwise, if subCollection is empty, return null.

5. Otherwise, return subCollection.

To get the "all"-indexed or named element(s) from an HTMLAllCollection collection given nameOrIndex:

1. 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.

2. Return the result of getting the "all"-named element(s) from collection given nameOrIndex.

2.6.2.1.1 [[Call]] ( thisArgument, argumentsList )

1. If argumentsList's size is zero, or if argumentsList[0] is undefined, return null.

2. Let nameOrIndex be the result of converting argumentsList[0] to a DOMString.

3. Let result be the result of getting the "all"-indexed or named element(s) from this HTMLAllCollection given nameOrIndex.

4. 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.)

2.6.2.2 The HTMLFormControlsCollection interface

The HTMLFormControlsCollection interface is used for collections of listed elements in forms.

[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.length

Returns the number of elements in collection.

element = collection.item(index)

element = collection[index]

Returns the item at index index in collection. The items are sorted in tree order.

element = collection.namedItem(name)

✔MDN

HTMLFormControlsCollection/namedItem

Support in all current engines.

Firefox33+Safari7+Chrome25+

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Opera15+Edge79+

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Edge (Legacy)NoInternet ExplorerNo

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Firefox Android33+Safari iOS7+Chrome Android25+WebView Android37+Samsung Internet1.5+Opera Android14+

radioNodeList = collection.namedItem(name)

element = collection[name]

radioNodeList = collection[name]

Returns the item with ID or name name from collection.

If there are multiple matching items, then a RadioNodeList object containing all those elements is returned.

radioNodeList.value

Returns the value of the first checked radio button represented by radioNodeList.

radioNodeList.value = value

Checks the first first radio button represented by radioNodeList that has value value.

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:

1. If name is the empty string, return null and stop the algorithm.
2. If, at the time the method is called, there is exactly one node in the collection that has either an id attribute or a name attribute equal to name, then return that node and stop the algorithm.
3. Otherwise, if there are no nodes in the collection that have either an id attribute or a name attribute equal to name, then return null and stop the algorithm.
4. Otherwise, create a new 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.
5. Return that RadioNodeList object.

Members of the RadioNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object.

The value IDL attribute on the RadioNodeList object, on getting, must return the value returned by running the following steps:

1. 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.

2. If element is null, return the empty string.

3. If element is an element with no value attribute, return the string "on".

4. Otherwise, return the value of element's value attribute.

On setting, the value IDL attribute must run the following steps:

1. 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.

2. If element is not null, then set its checkedness to true.

2.6.2.3 The HTMLOptionsCollection interface

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.

[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.length

Returns the number of elements in collection.

collection.length = value

When set to a smaller number than the existing length, truncates the number of option elements in the container corresponding to collection.

When set to a greater number than the existing length, adds new blank option elements to the container corresponding to collection.

element = collection.item(index)

element = collection[index]

Returns the item at index index in collection. The items are sorted in tree order.

collection[index] = element

When index is a greater number than the number of items in collection, adds new blank option elements in the corresponding container.

When set to null, removes the item at index index from collection.

When set to an option element, adds or replaces it at index index in collection.

element = collection.namedItem(name)

element = collection[name]

Returns the item with ID or name name from collection.

If there are multiple matching items, then the first is returned.

collection.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 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.

Throws a "HierarchyRequestError" DOMException if element is an ancestor of the element into which it is to be inserted.

collection.remove(index)

Removes the item with index index from collection.

collection.selectedIndex

Returns the index of the first selected item, if any, or −1 if there is no selected item.

collection.selectedIndex = index

Changes the selection to the option element at index index in collection.

The object's supported property indices are as defined for HTMLCollection objects.

On getting, the length attribute must return the number of nodes represented by the collection.

On setting, the behavior depends on whether the new value is equal to, greater than, or less than the number of nodes represented by the collection at that time. If the number is the same, then setting the attribute must do nothing. If the new value is greater, then n new option elements with no attributes and no child nodes must be appended to the select element on which the HTMLOptionsCollection is rooted, where n is the difference between the two numbers (new value minus old value). Mutation events must be fired as if a DocumentFragment containing the new option elements had been inserted. If the new value is lower, then the last n nodes in the collection must be removed from their parent nodes, where n is the difference between the two numbers (old value minus new value).

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:

1. If value is null, invoke the steps for the remove method with index as the argument, and return.

2. Let length be the number of nodes represented by the collection.

3. Let n be index minus length.

4. 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.

5. 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:

1. If element is an ancestor of the select element on which the HTMLOptionsCollection is rooted, then throw a "HierarchyRequestError" DOMException.

2. 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.

3. If element and before are the same element, then return.

4. 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.

5. 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.

6. Pre-insert element into parent node before reference.

The remove(index) method must act according to the following algorithm:

1. If the number of nodes represented by the collection is zero, return.

2. If index is not a number greater than or equal to 0 and less than the number of nodes represented by the collection, return.

3. Let element be the indexth element in the collection.

4. 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

2.6.3 The DOMStringList interface

The DOMStringList interface is a non-fashionable retro way of representing a list of strings.

[Exposed=(Window,Worker)]
interface DOMStringList {
  readonly attribute unsigned long length;
  getter DOMString? item(unsigned long index);
  boolean contains(DOMString string);
};

New APIs must use sequence<DOMString> or equivalent rather than DOMStringList.

strings.length

Returns the number of strings in strings.

strings[index]

strings.item(index)

Returns the string with index index from strings.

strings.contains(string)

Returns true if strings contains string, and false otherwise.

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.

The length getter steps are to return this's associated list's size.

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.

The contains(string) method steps are to return true if this's associated list contains string, and false otherwise.