Detailed explanation of HTML5 universal interface

1. Let’s talk about a few basic types first: DOMString, boolean, long, unsigned long, double,

NaN (Not-a-Number).

DOMString is actually a string in other commonly used languages. In HTML5, it is used to represent urls, Dom content, etc. Other boolean (Boolean), long (long integer), unsigned long (unsigned long integer), double (floating point number) I don’t think I need to elaborate on it, everyone can understand it. As for NaN, I think most JS veterans know its meaning, which is an infinite

or non-numeric value.

The official documents do not introduce undefined and null. As for why, I hope an expert can give an answer~~

2. Collection types include:

HTMLCollection, HTMLAllCollection,
HTMLFormControlsCollection, HTMLOptionsCollection, and
HTMLPropertiesCollection。

HTMLCollection is a generic collection and the basic interface of a collection. It provides three attributes:
length, item, namedItem.

length is the length of the collection.
item(index) can use the index value to get the elements in the collection.
namedItem(name) can get the element by its name.

In fact, you can also directly use collection[index], collection(index) or collection

[name], collection(name) to get the elements in the collection.

HTMLAllCollection inherits from the HTMLCollection interface, which contains the following attributes:

The length and item attributes are the same as those of HTMLCollection.

The difference between namedItem(name) and HTMLCollection is that it may return a collection.

tags(tagname) returns a collection with tagname.

Similarly, you can also directly use collection[index], collection(index) or collection

[name], collection(name) to get the elements in the collection. When the value matches multiple elements Returns a

HTMLAllCollection.

HTMLFormControlsCollection is a collection with form and fieldset as elements. Also inherited from

HTMLCollection interface.

Has all the properties of HTMLCollection, and also adds the RadioNodeList interface. It inherits from NodeList.

In fact, RadioNodeList is by definition a collection of Radiobuttons. I'm more curious about the purpose of putting such a list

in HTMLFormControlsCollection.

HTMLOptionsCollection is a collection of options, inherited from the HTMLCollection interface, which is generally used

to manipulate the child elements of the select tag.

The unique attributes of HTMLOptionsCollection are: add (option), remove (index), selectedIndex

The add method has two overloads

void add(in HTMLElement element, in optional HTMLElement before);
void add(in HTMLElement element, in long before);

To add an element, the first parameter is required, and the following parameters are optional.

remove(index) deletes an element by index.

selectedIndex I believe everyone can understand it.

The above is the detailed explanation of the HTML5 universal interface. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!