A guide to using JavaScript to restrict the textarea's height while allowing it to expand dynamically and setting a maximum height

Question

A guide to using JavaScript to restrict the textarea's height while allowing it to expand dynamically and setting a maximum height

Seeking assistance with a challenge I have encountered and unsure how to resolve. Any help would be greatly appreciated!

The issue at hand is as follows:

I am currently working on a textarea. My goal is to have the input box start with a height of 36px, but as text is inputted, the height of the box should expand to 72px. However, the maximum height should be capped at 72px and not increase further with additional text input.

The above is what I am aiming to achieve. As I am still new to programming, I am unsure if this can be accomplished through CSS alone or if JavaScript is required. How can I fulfill this requirement using JavaScript?

Thank you to everyone who takes the time to read my question and offer assistance. Your help is much appreciated.

Code Snippet:


        body {
          min-height: 100vh;
          display: flex;
          justify-content: center;
          align-items: center;
        }
        ... (remaining CSS code)


        <div class="demo">
          <div class="wrap">
            <ul class="tool">
              <li>photo</li>
              <li>file</li>
              <li>example</li>
            </ul>
            <textarea class="chat"></textarea>
            <div class="tool__footer">
              <input type="checkbox" id="enter"><label for="enter">ENTER</label>
              <a type="text" class="send" href="javascript:;">send</a>
            </div>
          </div>
        </div>

https://i.sstatic.net/FMlkX.png

javascript css

Answer 1

Answer №1

An easy fix by counting the number of line breaks:

function adjustTextareaHeight(value) {
  let linebreaks = (value.match(/\n/g) || []).length-1
  // calculate height based on line breaks
  let height = 36 + (linebreaks * 20)
  return height;
}

let textarea = document.querySelector(".chat");
textarea.addEventListener("input", () => {
  let height = adjustTextareaHeight(textarea.value);
  // Set minimum height to 36px
  if (height<36){
  textarea.style.height = '36px'
  } else {
   // Cap height at 72px
    textarea.style.height = height >72 ?"72px" :height + "px";
  }
});

.chat{
height:36px;
/* Add transition for smooth resizing */
transition:all 0.2s;
}

<!-- Use wrap="off" for rows=newlines behavior -->
<textarea wrap="off" class="chat"></textarea>

Answer 2

An easy fix by counting the number of line breaks:

function adjustTextareaHeight(value) {
  let linebreaks = (value.match(/\n/g) || []).length-1
  // calculate height based on line breaks
  let height = 36 + (linebreaks * 20)
  return height;
}

let textarea = document.querySelector(".chat");
textarea.addEventListener("input", () => {
  let height = adjustTextareaHeight(textarea.value);
  // Set minimum height to 36px
  if (height<36){
  textarea.style.height = '36px'
  } else {
   // Cap height at 72px
    textarea.style.height = height >72 ?"72px" :height + "px";
  }
});

.chat{
height:36px;
/* Add transition for smooth resizing */
transition:all 0.2s;
}

<!-- Use wrap="off" for rows=newlines behavior -->
<textarea wrap="off" class="chat"></textarea>

Answer 3

Answer №2

Solution

A simple oninput event handler can be used to resize the textarea dynamically with every new input. This technique was inspired by a solution from .

<textarea class="chat" oninput="this.style.height = ''; this.style.height = Math.min(this.scrollHeight - 4, 72) + 'px'"></textarea>

Explanation

Each time a new input is provided, the height of the textarea is set to the minimum value between its scrollHeight (the space needed to display the entire content) and 72 pixels. It is essential to account for the padding when calculating the new height, as scrollHeight includes the padding of the textarea while the height does not. The usual padding for textareas is 2 pixels (total 4 pixels for top and bottom), hence the need to adjust by 4 pixels with this.scrollHeight - 4. For a different padding value, the subtraction should be adjusted accordingly.

Your example

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.demo {
  width: 100%;
  padding: 16px;
  border: 1px solid #222;
  box-sizing: border-box;
}
.demo .tool {
  display: flex;
  list-style-type:none;
}
.demo .tool li {
  padding: 16px;
  background-color: #ccc;
  border: 1px solid #222;
}
.demo .chat {
  margin-top: 16px;
  width: 100%;
  height: 36px;
}
.demo .tool__footer {
  margin: 16px;
}
.demo .tool__footer .send {
  text-decoration: none;
  padding: 8px;
  background-color: #f9cf5a;
  color: #222;
  border-radius: 6px;
}

<div class="demo">
  <div class="wrap">
     <ul class="tool">
        <li>photo</li>
        <li>file</li>
        <li>example</li>
     </ul>
    <textarea class="chat" oninput="this.style.height = ''; this.style.height = Math.min(this.scrollHeight - 4, 72) + 'px'"></textarea>
    <div class="tool__footer">
       <input type="checkbox" id="enter"><label for="enter">ENTER</label>
       <a type="text" class="send" href="javascript:;">send</a>
    </div>
  </div>
</div>

Answer 4

Solution

A simple oninput event handler can be used to resize the textarea dynamically with every new input. This technique was inspired by a solution from .

<textarea class="chat" oninput="this.style.height = ''; this.style.height = Math.min(this.scrollHeight - 4, 72) + 'px'"></textarea>

Explanation

Each time a new input is provided, the height of the textarea is set to the minimum value between its scrollHeight (the space needed to display the entire content) and 72 pixels. It is essential to account for the padding when calculating the new height, as scrollHeight includes the padding of the textarea while the height does not. The usual padding for textareas is 2 pixels (total 4 pixels for top and bottom), hence the need to adjust by 4 pixels with this.scrollHeight - 4. For a different padding value, the subtraction should be adjusted accordingly.

Your example

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.demo {
  width: 100%;
  padding: 16px;
  border: 1px solid #222;
  box-sizing: border-box;
}
.demo .tool {
  display: flex;
  list-style-type:none;
}
.demo .tool li {
  padding: 16px;
  background-color: #ccc;
  border: 1px solid #222;
}
.demo .chat {
  margin-top: 16px;
  width: 100%;
  height: 36px;
}
.demo .tool__footer {
  margin: 16px;
}
.demo .tool__footer .send {
  text-decoration: none;
  padding: 8px;
  background-color: #f9cf5a;
  color: #222;
  border-radius: 6px;
}

<div class="demo">
  <div class="wrap">
     <ul class="tool">
        <li>photo</li>
        <li>file</li>
        <li>example</li>
     </ul>
    <textarea class="chat" oninput="this.style.height = ''; this.style.height = Math.min(this.scrollHeight - 4, 72) + 'px'"></textarea>
    <div class="tool__footer">
       <input type="checkbox" id="enter"><label for="enter">ENTER</label>
       <a type="text" class="send" href="javascript:;">send</a>
    </div>
  </div>
</div>

A guide to using JavaScript to restrict the textarea's height while allowing it to expand dynamically and setting a maximum height

Answer №1

Answer №2

Solution

Explanation

Your example

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