Auto Expand Textarea

Auto expand textarea implementation using HTML, CSS, and JavaScript, perfect for enhancing user experience with text input fields that automatically adjust their size based on content.

Learn how to implement auto expand textarea functionality using a combination of HTML, CSS, and JavaScript, providing a seamless solution for creating text input fields that dynamically adjust their size as users type. Auto expand textareas offer a user-friendly experience by eliminating the need for manual resizing and ensuring that all text content remains visible.

With HTML, CSS, and JavaScript, you can create auto expand textareas with responsive behavior and customizable styles. Define the textarea structure in HTML, style it with CSS to match your website's design language, and add functionality with JavaScript to enable dynamic resizing based on text input.

Implementing auto expand textareas with HTML, CSS, and JavaScript enhances usability and accessibility by providing a fluid and intuitive text input experience. Users can easily input and edit text content without constraints, resulting in a more efficient and enjoyable interaction with your website.

Integrating auto expand textareas into your website using HTML, CSS, and JavaScript is straightforward and well-documented, making it accessible to developers of all levels. Whether you're building a blog, a messaging app, or a form-based application, auto expand textareas offer a practical solution for improving text input functionality.

Enhance user experience and streamline text input on your website by incorporating auto expand textareas using HTML, CSS, and JavaScript. Provide users with a seamless and responsive text input experience, ensuring that text content remains visible and accessible at all times.

Steps to Copy the Code

Creating a customized Auto Expand Textarea with HTML, CSS, and JavaScript is made simple with our comprehensive guide. Follow these steps to copy the code and personalize it to match your website's design:

  1. Copy the Code: Start by copying the HTML, CSS, and JavaScript code for the Auto Expand Textarea component from our guide or relevant documentation.
  2. Paste into Your Project: Open your project files in a code editor and paste the copied HTML, CSS, and JavaScript code into the appropriate files. Paste the HTML code into your HTML file at the desired location where you want the Auto Expand Textarea to appear. Paste the CSS code into your CSS file, and the JavaScript code into your JavaScript file.
  3. Customize as Needed: HTML, CSS, and JavaScript provide flexibility for customizing the appearance and behavior of your Auto Expand Textarea. Modify the code to match your design preferences, such as adjusting colors, sizes, and styles for the textarea element and its container. You can also tweak the JavaScript code to change the behavior of the textarea as needed.
  4. Test and Refine: After making modifications, thoroughly test the Auto Expand Textarea in various browsers and screen sizes to ensure it functions as expected. Make any necessary adjustments to refine its behavior and responsiveness.
  5. Enhance with Interactivity (Optional): Consider adding additional interactivity to your Auto Expand Textarea using JavaScript, such as implementing character limits or validation.

By following these steps, you'll be able to effectively customize an Auto Expand Textarea component using HTML, CSS, and JavaScript, allowing you to create a seamless and user-friendly text input experience for your website visitors.

Code Explanation


<textarea class='autoExpand' rows='3' data-min-rows='3' placeholder='Auto-Expanding Textarea' autofocus></textarea>
  • class='autoExpand': This assigns the class "autoExpand" to the textarea element. This class is likely used to apply specific styling or functionality to the textarea, such as auto-expanding behavior.
  • rows='3': This sets the initial number of visible rows in the textarea to 3. The textarea will display three lines of text by default.
  • data-min-rows='3': This custom attribute (data-min-rows) specifies the minimum number of rows the textarea should expand to accommodate its content. In this case, it's set to 3, which means that the textarea will always display at least three rows, even if there's no content inside.
  • placeholder='Auto-Expanding Textarea': This sets the placeholder text that appears in the textarea when it's empty. In this case, it's set to "Auto-Expanding Textarea", indicating to the user what type of content is expected.
  • autofocus: This attribute automatically focuses on the textarea element when the page loads, meaning that the cursor will be placed inside the textarea ready for user input without the need for additional interaction.

CSS Code

1. Resetting Default Margins and Setting Full Height:

html, body {
  margin: 0;
  height: 100%;
  • This rule removes any default margins from the html and body elements and ensures that they take up the full height of the viewport.

2. Styling the Body:

body {
  background: #87b48e;
  display: flex;
  align-items: center;
  • This rule sets the background color of the body to a light green shade (#87b48e).
  • It uses flexbox (display: flex;) to horizontally center its child elements.
  • align-items: center; aligns the child elements vertically at the center of the body.

3. Styling the Textarea:

textarea {
  display: block;
  box-sizing: padding-box;
  overflow: hidden;
  padding: 10px;
  width: 250px;
  font-size: 14px;
  margin: 50px auto;
  border-radius: 6px;
  box-shadow: 2px 2px 8px rgba(0, 0, 0, 0.3);
  border: 0;
  • This rule styles the textarea element.
  • display: block; ensures that the textarea is displayed as a block element.
  • box-sizing: padding-box; specifies that padding and border sizes should be included in the textarea's width and height.
  • overflow: hidden; hides any content that exceeds the textarea's dimensions.
  • padding: 10px; adds 10 pixels of padding inside the textarea.
  • width: 250px; sets the initial width of the textarea to 250 pixels.
  • font-size: 14px; sets the font size of the text inside the textarea to 14 pixels.
  • margin: 50px auto; adds a top and bottom margin of 50 pixels and horizontally centers the textarea using the automatic left and right margins.
  • border-radius: 6px; rounds the corners of the textarea.
  • box-shadow: 2px 2px 8px rgba(0, 0, 0, 0.3); apply a shadow effect to the textarea, providing a subtle depth effect.
  • border: 0; removes the default border of the textarea.

4. Focus Styles for Textarea:

textarea:focus {
  border: none;
  outline: none;
  • This rule removes the border and outline styles when the textarea is in focus, giving it a cleaner appearance.

JavaScript Code

function getScrollHeight(elm){
  var savedValue = elm.value;
  elm.value = '';
  elm._baseScrollHeight = elm.scrollHeight;
  elm.value = savedValue;

This function calculates the base scroll height of a textarea element (elm) by temporarily clearing its value, measuring its scroll height, and then restoring the original value. This is achieved by:

  • Saving the current value of the textarea in a variable (savedValue).
  • Setting the value of the textarea to an empty string to clear its content.
  • Storing the scroll height of the textarea in a custom property _baseScrollHeight.
  • Restoring the original value of the textarea.
function onExpandableTextareaInput({ target: elm }){
  if( !elm.classList.contains('autoExpand') || !elm.nodeName == 'TEXTAREA' ) return;
  var minRows = elm.getAttribute('data-min-rows') | 0, rows;
  !elm._baseScrollHeight && getScrollHeight(elm);
  elm.rows = minRows;
  rows = Math.ceil((elm.scrollHeight - elm._baseScrollHeight) / 16);
  elm.rows = minRows + rows;
  • This function is the event handler for the input event on textarea elements.
  • It checks if the input event target (elm) is a textarea element with the class autoExpand.
  • If the conditions are met, it calculates the number of rows needed to display the textarea content based on its scroll height.
  • The number of rows is determined by subtracting the base scroll height (elm._baseScrollHeight) from the current scroll height of the textarea and dividing the result by the estimated height of a single row (16 pixels).
  • The textarea's rows attribute is then updated to accommodate the calculated number of rows.
document.addEventListener('input', onExpandableTextareaInput);
  • This line adds an event listener to the document for the input event, which fires whenever the value of an input or textarea element changes.
  • When the input event occurs, the onExpandableTextareaInput function is called, providing the textarea element that triggered the event as the target parameter.