HTML - DOM Attribute isId Property

Quiz

HTML DOM attribute isId property is used to determine whether a HTML attribute is an 'id' attribute or not. The isId property is available on objects that implement the Attr interface.

In the context of HTML, an id is used to uniquely identify an element within an HTML document, allowing for targeted styling, scripting, and linking.

The isId attribute is deprecated and no longer supported in modern browsers. If you try to access this attribute browser will return value 'undefined'. Alternatively you can use HTML DOM attribute name property to get name of the attribute and check if it is 'id'

Syntax

attribute.isId

Return value

It returns boolean value. True if 'id' attribute is present else it returns false. In modern browsers it will return 'undefined' as mentioned above.

Examples of HTML isId DOM Attribute

Here are few example codes that illustrate how to use isId attribute in HTML and JavaScript.

Check presence of ID attribute

This is a sample code that check if id attribute present on div tag. The element.attributes accesses the attributes property of a DOM element, which is a collection (NamedNodeMap) of all attribute nodes registered to the element. And the element.attributes[0] accesses the first attribute node in the collection of attributes of the element.

<!DOCTYPE html>
<html>

<head>
    <title>HTML DOM Attribute isId Property</title>
</head>

<body>
    <h3>HTML DOM Attribute isId Property</h3>
    <p>The attribute of Div element: </p>
    <div id="demo"></div>
    <script>
        const ele = document.getElementById("demo");

        // This will select 1st attribute of 'ele' element
        const answer = ele.attributes[0].isId;
        // Pass the name to inside of div tag
        element.innerHTML = answer;
    </script>
    <p>
        The isId property is deprecated, You can't 
        see the value returned by isId property.
    </p>
</body>

</html>

Alternative for isId attribute

The HTML DOM property 'name' can be used alternative to 'isId' property. This will return name of attribute of the tag mentioned. Following code shows how to use this property in HTML and JavaScript.

<!DOCTYPE html>
<html>

<head>
    <title>HTML DOM Attribute isId Property</title>
</head>

<body>
    <h3>HTML DOM Attribute isId Property</h3>
    <p>
        The name property of DOM returns 
        the name of an attribute
    </p>
    <div id="demo"></div>
    <script>
        const element = document.getElementById("demo");

        //This will select name of first attribute of div
        let aName = element.attributes[0].name;
        //Pass the name to inside of div tag
        document.getElementById("demo").innerHTML = aName;
    </script>
</body>

</html>

Supported Browsers

Property
isId	No	No	No	No	No

html_dom.htm

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