Can I add a custom attribute to an HTML tag?

The Question :

360 people think this question is useful

Can I add a custom attribute to an HTML tag like the following?

<tag myAttri="myVal" />

The Question Comments :

The Answer 1

193 people think this answer is useful

You can amend your !DOCTYPE declaration (i.e. DTD) to allow it, so that the [XML] document will still be valid:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
[
  <!ATTLIST tag myAttri CDATA #IMPLIED>
]>

#IMPLIED means it is an optional attribute, or you could use #REQUIRED, etc.

More information is in DTD – Attributes.

The Answer 2

311 people think this answer is useful

You can add custom attributes to your elements at will. But that will make your document invalid.

In HTML 5 you will have the opportunity to use custom data attributes prefixed with data-.

The Answer 3

78 people think this answer is useful

No, this will break validation.

In HTML 5 you can/will be able to add custom attributes. Something like this:

<tag data-myAttri="myVal" />

The Answer 4

33 people think this answer is useful

The jQuery data() function allows you to associate arbitrary data with DOM elements. Here’s an example.

The Answer 5

24 people think this answer is useful

In HTML5: yes: use the data- attribute.

 <ul>
  <li data-animal-type="bird">Owl</li>
  <li data-animal-type="fish">Salmon</li>
  <li data-animal-type="spider">Tarantula</li>
</ul> 

The Answer 6

14 people think this answer is useful

Yes, you can do it!

Having the next HTML tag:

<tag key="value"/>

We can access their attributes with JavaScript:

element.getAttribute('key'); // Getter
element.setAttribute('key', 'value'); // Setter

Element.setAttribute() put the attribute in the HTML tag if not exist. So, you dont need to declare it in the HTML code if you are going to set it with JavaScript.

key: could be any name you desire for the attribute, while is not already used for the current tag. value: it’s always a string containing what you need.

The Answer 7

10 people think this answer is useful

Yes, you can, you did it in the question itself: <html myAttri="myVal"/>.

The Answer 8

9 people think this answer is useful

var demo = document.getElementById("demo")
console.log(demo.dataset.myvar)
// or
alert(demo.dataset.myvar)
//this will show in console the value of myvar
<div id="demo" data-myvar="foo">anything</div>

The Answer 9

7 people think this answer is useful

You can set properties from JavaScript.

document.getElementById("foo").myAttri = "myVal"

The Answer 10

4 people think this answer is useful

Here is the example:

document.getElementsByTagName("html").foo="bar"

Here is another example how to set custom attributes into body tag element:

document.getElementsByTagName('body')[0].dataset.attr1 = "foo";
document.getElementsByTagName('body')[0].dataset.attr2 = "bar";

Then read the attribute by:

attr1 = document.getElementsByTagName('body')[0].dataset.attr1
attr2 = document.getElementsByTagName('body')[0].dataset.attr2


You can test above code in Console in DevTools, e.g.

JS Console, DevTools in Chrome

The Answer 11

1 people think this answer is useful

use data-any , I use them a lot

<aside data-area="asidetop" data-type="responsive" class="top">

The Answer 12

1 people think this answer is useful

well! you can actually create a bunch of custom HTML attributes by disguising the data attributes in what you actually want.

eg.

[attribute='value']{
color:red;
}

<span attribute="value" >hello world</span>

It apparently works but that would invalidate your document, there is no need of using JScript for you to have custom attributes or even elements unless you have to, you just need to treat your new formulated(custom) attributes just the same way you treat your “data” attribute

Remember “invalid” does not mean anything. The document will load fine at all the time. and some browsers would actually validate your document only by the presence of DOCTYPE….., you actually know what I mean.

The Answer 13

0 people think this answer is useful

Another approach, which is clean and will keep the document valid, is to concatenate the data you want into another tag e.g. id, then use split to take what you want when you want it.

<html>
<script>
  function demonstrate(){
    var x = document.getElementById("example data").querySelectorAll("input");
    console.log(x);
    for(i=0;i<x.length;i++){
      var line_to_illustrate = x[i].id  + ":" + document.getElementById ( x[i].id ).value;
      //concatenated values
      console.log("this is all together: " + line_to_illustrate); 
      //split values
      var split_line_to_illustrate = line_to_illustrate.split(":");
      for(j=0;j<split_line_to_illustrate.length;j++){
        console.log("item " + j+ " is: " + split_line_to_illustrate[j]);
      }      
    }
  }
</script> 

<body>

<div id="example data">
  <!-- consider the id values representing a 'from-to' relationship -->
  <input id="1:2" type="number" name="quantity" min="0" max="9" value="2">
  <input id="1:4" type="number" name="quantity" min="0" max="9" value="1">
  <input id="3:6" type="number" name="quantity" min="0" max="9" value="5">  
</div>

<input type="button" name="" id="?" value="show me" onclick="demonstrate()"/>

</body>
</html>

The Answer 14

0 people think this answer is useful

Yes, you can use data-* attribute. The data-* attribute is used to store custom data private to the page or application.

<ul>
    <li data-pageNumber="1"> 1 </li>
    <li data-pageNumber="2"> 2 </li>  
    <li data-pageNumber="3"> 3 </li>  
</ul

The Answer 15

0 people think this answer is useful

I can think of a handy use for the custom tag "init". Include a JavaScript expression that gets evaluated at document.onLoad() time and provides a value for the tag, e.g.

<p>&amp;lt;p&amp;gt;The UTC date is &amp;lt;span init="new Date().toUTCString()"&amp;gt;?&amp;lt;/span&amp;gt;.&amp;lt;p&amp;gt;</p>

Some boilerplate JavaScript code would scan all the tags in the DOM at document.onload() time looking for the init attributes, evaluating the expressions that they contain, and assigning them to the containing tag’s innerHTML. This would give HTML some of the power of JSP, PHP etc. Currently we have to split the HTML markup and the JavaScript code that illuminates it. Bugs love split code.

The Answer 16

-1 people think this answer is useful

You can add, but then you have to write a line of JavaScript code too,

document.createElement('tag');

to make sure everything fall in place. I mean Internet Explorer 🙂

The Answer 17

-9 people think this answer is useful

You can do something like this to extract the value you want from JavaScript instead of an attribute:

<a href='#' class='click'>
    <span style='display:none;'>value for JavaScript</span>some text
</a>

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