HTML id Attribute
The HTML id attribute is used to specify a unique id for an HTML element.
You cannot have more than one element with the same id in an HTML document. It is just like the unique name specified to element, which we can use to access it in CSS Styles or JavaScript Code.
Using The id Attribute
The id attribute specifies a unique id for an HTML element. The value of the id attribute must be unique within the HTML document.
The id attribute is used to point to a specific CSS style declaration. It is also used by JavaScript to access and manipulate the element with the specific id.
The syntax for id is: write a hash character (#), followed by an id name. Then, define the CSS properties within curly braces {}.
In the following example we have an <h1> element that points to the id name "myHeader". This <h1> element will be styled according to the #myHeader style definition in the head section:
Example
<!DOCTYPE html>
<html>
<head>
<style>
#myHeader {
background-color: lightblue;
color: black;
padding: 40px;
text-align: center;
}
</style>
</head>
<body>
<h1 id="myHeader">My Header</h1>
</body>
</html>
My Header
Note: The id name is case sensitive!
Note: The id name must contain at least one character, cannot start with a number, and must not contain whitespaces (spaces, tabs, etc.).
Difference Between Class and ID
A class name can be used by multiple HTML elements, while an id name must only be used by one HTML element within the page:
Example
<style>
/* Style the element with the id "myHeader" */
#myHeader {
background-color: lightblue;
color: black;
padding: 40px;
text-align: center;
}
/* Style all elements with the class name "city" */
.city {
background-color: tomato;
color: white;
padding: 10px;
}
</style>
<!-- An element with a unique id -->
<h1 id="myHeader">My Cities</h1>
<!-- Multiple elements with same class -->
<h2 class="city">London</h2>
<p>London is the capital of England.</p>
<h2 class="city">Paris</h2>
<p>Paris is the capital of France.</p>
<h2 class="city">Tokyo</h2>
<p>Tokyo is the capital of Japan.</p>
My Cities
London
London is the capital of England.
Paris
Paris is the capital of France.
Tokyo
Tokyo is the capital of Japan.
HTML Bookmarks with ID and Links
HTML bookmarks are used to allow readers to jump to specific parts of a webpage.
Bookmarks can be useful if your page is very long.
To use a bookmark, you must first create it, and then add a link to it.
Then, when the link is clicked, the page will scroll to the location with the bookmark.
Example
First, create a bookmark with the id attribute:
<h2 id="C4">Chapter 4</h2>
Chapter 4
Then, add a link to the bookmark ("Jump to Chapter 4"), from within the same page:
Example
<a href="#C4">Jump to Chapter 4</a>
Jump to Chapter 4Or, add a link to the bookmark ("Jump to Chapter 4"), from another page:
<a href="/2022/08/html-id-attribute.html#C4">Jump to Chapter 4</a>
Jump to Chapter 4Using The id Attribute in JavaScript
The id attribute can also be used by JavaScript to perform some tasks for that specific element.
JavaScript can access an element with a specific id with the getElementById() method:
Example
Use the id attribute to manipulate text with JavaScript:
<script>
function displayResult() {
document.getElementById("myHeader1").innerHTML = "Have a nice day!";
}
</script>
Chapter Summary
- The id attribute is used to specify a unique id for an HTML element
- The value of the id attribute must be unique within the HTML document
- The id attribute is used by CSS and JavaScript to style/select a specific element
- The value of the id attribute is case sensitive
- The id attribute is also used to create HTML bookmarks
- JavaScript can access an element with a specific id with the getElementById() method
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