Example introduction to the difference between id and name attributes in input_HTML/Xhtml_Web page production

I have been building a website for a long time, but I still haven’t figured out the difference between name and id in input. I recently learned jquery and encountered this problem again, so I collected information online. After seeing this article, I sorted it out for later use.

It can be said that almost everyone who has done web development has asked, what is the difference between the ID and Name of an element? Why do we need Name when we have ID?! And we can also get the most classical answer: ID is like a person's ID number, and Name is like his name. ID is obviously unique, and Name is repeatable.

Last week I also encountered the problem of ID and Name. I entered an input type="hidden" on the page and only wrote an ID='SliceInfo'. After assigning the value, submit and use Request in the background. Params["SliceInfo"] cannot get the value. Later, I suddenly realized that it should be marked with Name, so I added Name='SliceInfo' to the input, and everything was ok.

The answer to ID and Name in the first paragraph is too general. Of course, that explanation is completely correct for ID, which is the Identity of the HTML element on the client side. Name is actually much more complicated, because Name has many uses, so it cannot be completely replaced by ID, thus canceling it. Specific uses are:

Use 1: As a server-side indicator of HTML elements that can interact with the server, such as input, select, textarea, and button. We can get the value submitted by the element through Request.Params based on its Name on the server side.
Use 2: HTML element Input type='radio' grouping, we know that the radio button control is in the same grouping class, the check operation is mutex, only one radio can be selected at the same time, this grouping is based on the same Name attribute realized.
Use 3: Establish an anchor point in the page. We know that link is to obtain a page hyperlink. If you do not use the href attribute, use Name instead, such as: < ;a name="PageBottom">, we get a page anchor.
Use 4: Identity as an object, such as Applet, Object, Embed and other elements. For example, in an Applet object instance, we will use its Name to refer to the object.
Purpose 5: When associating between IMG elements and MAP elements, if you want to define the hotspot area of ​​IMG, you need to use its attribute usemap, so usemap="#name" (Name of the associated MAP element).
Use 6: Attributes of certain specific elements, such as attribute, meta and param. For example, define parameters for Object or in Meta.

Obviously these uses cannot be simply replaced by ID, so the difference between ID and Name of HTML elements is not the difference between ID number and name. They have different functions. .

Of course, the Name attribute of the HTML element can also play a role as an ID in the page, because in the DHTML object tree, we can use document.getElementsByName to obtain an object array containing all specified Name elements in the page. . There is another problem with the Name attribute. When we dynamically create an element that can contain the Name attribute, we cannot simply use the assignment element.name = "..." to add its Name. We must use document.createElement( when creating the Element. '') adds the Name attribute to the element. What does this mean? Just look at the example below to understand.

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The code is as follows:

var input = document.createElement('INPUT');
input.id = 'myId';
input.name = 'myName';
alert(input.outerHTML);

The result displayed in the message box is: .

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The code is as follows:

var input = document.createElement('');
input.id = 'myId';
alert(input.outerHTML);
< ; /script>

The result displayed in the message box is: .
The design of initializing the Name attribute is not a defect of IE, because MSDN says it should be done this way, but what is the principle of this design? I haven't thought too clearly yet.

By the way, what if there are n (n>1) HTML elements in the page with the same ID? How to reference them in DHTML objects? If we use ASPX pages, such a situation is not easy to happen, because the aspnet process does not allow non-unique IDs when processing aspx pages. This means that the page will throw an exception and cannot be rendered normally. If it is not a dynamic page and we insist on repeating the ID, what should we do with IE? At this time, we can still use document.getElementById to obtain objects, but we can only obtain the first object that appears during HTML Render among those objects with duplicate IDs. At this time, the repeated ID will automatically become an array when referenced, and the elements with repeated IDs will exist in the array in order of Render.

Form elements (form input textarea select) and frame elements (iframe frame) are named
These elements are related to form submission (frame elements act on the target of the form). On the receiving page of the form, only
Receive elements with name. Elements assigned ID cannot receive values ​​through the form. You can verify it yourself.
There is an exception: A can be assigned name as an anchor or ID

Of course, the above elements can also be assigned ID values. When assigning ID values, the method of referencing these elements will change.
Assign name: document.formName.inputName document.frames("frameName")
Assign ID: document.getElementById("inputID") document.all.frameID

Only IDs can be assigned but not names: (except for elements related to the form, only IDs can be assigned)
body li table tr td th p div span pre dl dt dd font b etc.