HTML id Attribute

Guest · Post by **Guest** » Fri Oct 27, 2023 8:05 am

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.

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 style declaration in a style sheet. 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>

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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>
<h1 id="myHeader">My
Cities</h1><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>

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Tip: You can learn much more about CSS in our CSS Tutorial.

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>

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>

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Or, add a link to the bookmark ("Jump to Chapter 4"), from another page:

<a href="html_demo.html#C4">Jump to Chapter 4</a>

Using 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("myHeader").innerHTML = "Have a nice day!";}
</script>

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Tip: Study JavaScript in the HTML JavaScript chapter, or in our
JavaScript Tutorial.

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

HTML Exercises

Test Yourself With Exercises

Exercise:
Add the correct HTML attribute to make the H1 element red.

<!DOCTYPE html>

<html>

<head>

<style>

#myheader {color:red;}

</style>

</head>

<body>

<h1 >My Home Page</h1>

</body>

</html>

Submit Answer »
Start the Exercise

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+1

Reference: https://www.w3schools.com/html/html_id.asp