A Textarea Element That Autoresizes

Due to the fact that the HTML <textarea> element does not automatically grow to fit its content, many developer look for plugins and scripts to enable this feature. This bit of JavaScript will cause any applicable <textarea> elements to resize automatically to fit the content typed or pasted into it.

The code has the following features:

  • Uses a hidden clone element (a <div>) that has the same typographical properties as the <textarea>
  • Has no dependencies (e.g. jQuery)
  • Will autosize any <textarea> that has a class of txta
  • Works in all browsers, even old IE

Here’s the HTML:

<textarea placeholder="Type multiple lines of content here." class="txta"></textarea>

Here’s the CSS:

.txta { width: 100%; max-width: 500px; min-height: 100px; font-family: Arial, sans-serif; font-size: 16px; overflow: hidden; line-height: 1.4; }

And the JavaScript (commented):

// Targets all textareas with class "txta" let textareas = document.querySelectorAll('.txta'), hiddenDiv = document.createElement('div'), content = null; // Adds a class to all textareas for (let j of textareas) { j.classList.add('txtstuff'); } // Build the hidden div's attributes // The line below is needed if you move the style lines to CSS // hiddenDiv.classList.add('hiddendiv'); // Add the "txta" styles, which are common to both textarea and hiddendiv // If you want, you can remove those from CSS and add them via JS hiddenDiv.classList.add('txta'); // Add the styles for the hidden div // These can be in the CSS, just remove these three lines and uncomment the CSS hiddenDiv.style.display = 'none'; hiddenDiv.style.whiteSpace = 'pre-wrap'; hiddenDiv.style.wordWrap = 'break-word'; // Loop through all the textareas and add the event listener for(let i of textareas) { (function(i) { // Note: Use 'keyup' instead of 'input' // if you want older IE support i.addEventListener('input', function() { // Append hiddendiv to parent of textarea, so the size is correct i.parentNode.appendChild(hiddenDiv); // Remove this if you want the user to be able to resize it in modern browsers i.style.resize = 'none'; // This removes scrollbars i.style.overflow = 'hidden'; // Every input/change, grab the content content = i.value; // Add the same content to the hidden div // This is for old IE content = content.replace(/\n/g, '<br>'); // The <br ..> part is for old IE // This also fixes the jumpy way the textarea grows if line-height isn't included hiddenDiv.innerHTML = content + '<br style="line-height: 3px;">'; // Briefly make the hidden div block but invisible // This is in order to read the height hiddenDiv.style.visibility = 'hidden'; hiddenDiv.style.display = 'block'; i.style.height = hiddenDiv.offsetHeight + 'px'; // Make the hidden div display:none again hiddenDiv.style.visibility = 'visible'; hiddenDiv.style.display = 'none'; }); })(i); }

The HTML in the demo also includes a commented-out second <textarea> element that you can uncomment to test multiple textareas on the same page.

Source

Note: To the best of our knowledge, the information above and the snippet are accurate and up to date. However, in case you notice something wrong, please report snippet or leave a comment below.
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