HTML - Global id Attribute

The id is an HTML global attribute that defines an identifier (id) that must be unique in the whole HTML document. Its purpose is to identify the element uniquely when linking with scripting or styling with CSS.

The id is mostly used with CSS and JavaScript to perform a certain task for a unique element.

The name of the id is referred to by the "#" keyword in CSS and Dom methods such as document.getElementById("id_name") in JavaScript.

Syntax

Following is the syntax of the id attribute −

<element id = "id_name" >

Example

In the following example, we are creating an HTML document and using the id attributes to style the content of the elements, as follows −

<!DOCTYPE html>
<html>
<head>
   <style>
      #exciting {
         background: linear-gradient(to bottom, #ffe8d4, #f69d3c);
         border: 1px solid #696969;
         padding: 10px;
         border-radius: 10px;
         box-shadow: 2px 2px 1px black;
      }

      #exciting:before {
         content: 'ℹ️';
         margin-right: 5px;
      }
   </style>
</head>
<body>
   <p>A normal, boring paragraph. Try not to fall asleep. </p>
   <p id="exciting">The most exciting paragraph on the page. One of a kind! </p>
</body>
</html>

When we run the above code, it will generate an output consisting of the text applied with CSS displayed on the webpage.

Example

Considering the another scenario, where we re going to use the id attribute

<!DOCTYPE html>
<html>
<head>
   <style>
      #brand {
         font-size: 30px;
         color: green;
      }

      #point {
         font-size: 26px;
         color: black;
      }

      #caption {
         font-size: 20px;
         font-style: italic;
      }
   </style>
</head>
<body>
   <p> This is example of class attribute</p>
   <h2 id="brand">tutorials <span id="point">point</span>
   </h2>
   <p id="caption">Easy to Learn!</p>
</body>
</html>

On running the above code, it will generate an output consisting of the text applied with CSS displayed on the webpage.

Example

Let's look into the following example, where we are going to run the script and using the id attribute

<!DOCTYPE html>
<html>
<head>
   <style></style>
</head>
<body>
   <p>This is a paragraph</p>
   <p id="myPara">Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s</p>
   <button type="button" onclick="changeBackground()">change background</button>
   <script>
      function changeBackground() {
         var para = document.getElementById("myPara");
         para.style.backgroundColor = "Blue";
      }
   </script>
</body>
</html>

When we execute the above script, the output window will pop up displaying the text along with a button on the webpage. when the user clicks on the button it gets triggered and changes the background color.

html_attributes_reference.htm
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