How to autosize a textarea using JavaScript

To autosize a textarea using JavaScript, you can utilize CSS properties and dynamically adjust the height of the textarea based on its content.

1. Retrieve the textarea element using JavaScript.
2. Add an event listener to the textarea to detect changes in its content.
3. On each change event, update the height of the textarea based on its scroll height.
4. Set the style of the textarea's height property to the scroll height to autosize it.

1. The code selects the textarea element using the querySelector() method.
2. An event listener is added to the textarea, listening for the input event which triggers whenever the content of the textarea changes.
3. On each input event, the height of the textarea is set to auto.
4. Then the scrollHeight property of the textarea is used to get the total height of the content and it is assigned as the new height of the textarea by setting the style.height property.

Example 2: Approach using a hidden div#

Another approach to autosize a textarea is by using a hidden div to calculate the required height based on the content.

1. The code creates a hidden div element using createElement() method.
2. The font properties (family, size, line height) and padding of the textarea are applied to the hidden div using getComputedStyle.
3. The hidden div is appended to the document body.
4. An event listener is added to the textarea to listen for the input event.
5. On each input event, the content of the textarea is copied to the hidden div.
6. The height of the textarea is set to match the height of the hidden div by setting the style.height property.

Example 3 : creating a pre element#

This approach creates a clone element with the same font properties and content as the textarea to calculate its height.

1. Create a clone element (pre).
2. Set the same font properties as the textarea.
3. Copy the content of the textarea to the clone element.
4. Append the clone element to the document body.
5. Set the height of the textarea to match the height of the clone element.

1. The code creates a clone element <pre> using createElement.
2. The font properties (family, size, line height) and padding of the textarea are applied to the clone element using getComputedStyle .
3. The clone element is appended to the document body.
4. An event listener is added to the textarea to listen for the input event.
5. On each input event, the content of the textarea is copied to the clone element.
6. The height of the textarea is set to match the height of the clone element by setting the style.height property.