JavaScript document.getElementById()

The JavaScript document.getElementById() method is used, when we need to get an HTML element using its ID value. For example:

HTML with JavaScript Code

<!DOCTYPE html>
<html>
<body>

   <p>The value is <span id="x"></span>.</p>
   
   <script>
      var element = document.getElementById("x");
      element.innerHTML = 10;
   </script>
   
</body>
</html>

Output

The value is .

Note - The innerHTML sets/returns HTML content to/of specified element.

In above example, using the following statement:

var element = document.getElementById("x");

The element whose ID value is x will be initialized to the element variable. And using the following statement:

element.innerHTML = 10;

The value 10 set as the content of returned element. In case, if the returned element using its ID value, already has some content, then the content will be removed and the new content using the innerHTML will get set to it.

The above example, can also be written in this way:

<!DOCTYPE html>
<html>
<body>

   <p>The value is <span id="x"></span>.</p>
   
   <script>
      document.getElementById("x").innerHTML = 10;
   </script>
   
</body>
</html>

JavaScript document.getElementById() Syntax

The syntax of document.getElementById() method in JavaScript, is:

document.getElementById(elementID)

The getElementById() function returns an Element object, if the specified elementID exists. Otherwise, returns null.

JavaScript document.getElementById() Example

The document.getElementById() method in JavaScript, is used when we need to edit (or apply styles to) an HTML element. For example, the following JavaScript program, changes the color of an HTML element whose ID value is cc:

HTML with JavaScript Code

<!DOCTYPE html>
<html>
<body>

   <p>The name of website is <span id="cc">fresherearth.com</span></p>
   
   <script>
      var element = document.getElementById("cc");
      element.style.color = "red";
   </script>
   
</body>
</html>

Output

The name of website is fresherearth.com

Note - If specified ID matches with multiple elements, then the first element will be returned. For example:

HTML with JavaScript Code

<!DOCTYPE html>
<html>
<body>

   <p>The name of website is <span id="100">fresherearth.com</span></p>
   <p>The name of website is <span id="100">fresherearth.com</span></p>
   
   <script>
      var element = document.getElementById("100");
      element.style.color = "red";
   </script>
   
</body>
</html>

Output

The name of website is fresherearth.com

Although, ID is unique, but we need to be aware, how the things work, when multiple elements exists with same ID.

Let me create another example of document.getElementById() method in JavaScript, where the color of text fresherearth.com changes, when user clicks on the button. Also, I've changed the font size of the text, before changing the color, by clicking on the button:

HTML with JavaScript Code

<!DOCTYPE html>
<html>
<body>

   <p id="1">fresherearth.com</p>
   <button onclick="chCol('red');">Change to Red</button>
   <button onclick="chCol('blue');">Change to Blue</button>
   <button onclick="chCol('yellow');">Change to Yellow</button>
   
   <script>
      var element = document.getElementById('1');
      element.style.fontSize = "1.4em";
      function chCol(newCol)
      {
         element.style.color = newCol;
      }
   </script>
   
</body>
</html>

Output

fresherearth.com

JavaScript Online Test

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