Javascript: setAttribute() v.s. element.attribute = value to set "name" attribute

Question

So I'm learning to manipulate the DOM and I noticed one interesting thing:

Let's say I want to set the name attribute of an element by using the "." dot notation:

element.name = "someName";
console.log(document.getElementsByName("someName")[0]); // returns "undefined"??

However if I use the document.setAttribute() method, it works fine:

element.setAttribute("name", "someName");
console.log(document.getElementsByName("someName")[0]); // returns the element like it should.

Not sure why the dot notation method doesn't work in the first case.

Why does this happen?

Solution 1

My guess (because you didn't specify the element type) is the element normally does not have a name attribute, so setting the DOM property like that won't work.

For example, setting the name property on an input element will work. Setting it on a div will not.

It will work, however, with setAttribute().

jsFiddle.

Solution 2

To extend the answers provided by some of the others ...

The attribute 'name' is only considered valid DOM for a few specific objects. According to https://developer.mozilla.org/en-US/docs/DOM/element.name those objects are:

 <a>, <applet>, <button>, <form>, <frame>, <iframe>, <img>, <input>, 
 <map>, <meta>, <object>, <param>, <select>, and <textarea>

For these objects you can set, get and change the name attribute using object.name BUT FOR ANY OTHER DOM OBJECT the attribute 'name' is a custom attribute and must be created using SetAttribute() or by adding it to the HTML declaration. Once it is created, you can acces it using setAttribute() and getAttribute() or you can refer to its value directly using object.attributes.name.value take a look at http://jsfiddle.net/radiotrib/yat72/1/ for an example. BTW - the alert box on load is intentional - check the code to see why ...

Solution 3

(Attempting to explain part of the above post a better, separately, since it is already went into -ve rating, and belief in that post will be less. Help improve this further if not better.)

*** The property

When you use, element.name, you are accessing an existing property named "name" or setting its value.

Example 1:
var div1 = document.getElementById("div1"); 
div1.textContent = "2";

*** The attribute

but, while using, element.setAttribute('name','someName'), you are actually setting the attribute named 'name'. This attribute can be an existing property OR a custom one we want:

Example 2:
var h1 = document.getElementById("H1"); 
h1.setAttribute("class", "democlass");

Example 3:
var d = document.getElementById("d1"); 
d.setAttribute("name1", "value1");

Comments

[Radiotrib]

partial answer ... limited and does not explain the reasoning behind the problem

[Suraj Jain]

Sir when I set some html element attribute as "undefined" , it does not work, and it continues to take its previous values. Can you tell me why is so ?

[user3167101]

@SurajJain Probably because the API doesn't allow the attribute to be undefined.

[Suraj Jain]

Almost a year passed .