css Flex div grow as child textarea grows (no jquery)

Question

Imagine I have the following

div{
  padding: 20px;
}

<div style="display:flex; background: gold; flex-direction: column;">
  <textarea>Do NOT expand this</textarea>
  <textarea class="expand">Expand this baby</textarea>

</div>

I want when content on textarea "expand" creates vertical overflow for it to expand parent div, not to create vertical scroll.

as you can read in the question above, i think this is not possible with only CSS unless you use a contenteditable div instead of textearea. — Temani Afif, Dec 25 '17 at 20:33
@TemaniAfif sure no prob, then a JS only solution but we are not using jquery — CommonSenseCode, Dec 25 '17 at 20:34

Temani Afif · Accepted Answer · 2017-12-25T20:43:10.913

I think this cannot be done with only CSS, and since you don't want a jQuery one, so here is a pure JS solution. The idea is to calculate the height (resize) the textarea each time you update the content

var tex = document.querySelector('textarea.expand');

tex.addEventListener('keydown', resize);

function resize() {
  setTimeout(function() {
    tex.style.height = 'auto'; //needed when you remove content so we reduce the height
    tex.style.height = tex.scrollHeight + 'px';
  }, 0);
}

div {
  padding: 20px;
}

<div style="display:flex; background: gold; flex-direction: column;">
  <textarea>Do NOT expand this</textarea>
  <textarea class="expand">Expand this baby</textarea>
</div>

css Flex div grow as child textarea grows (no jquery)

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