JSFiddle - React, Tailwind, and code Playground

by Ryan Britton

HTML

<div>
    <span>adslafk jdasjf kls fjsldajk <br/> fasdjk fjl;jkl fjklj kljkj<br/> fasdjk fjl;jkl fjklj kljkj<br/> fasdjk fjl;jkl fjklj kljkj<br/> fkl fjkljka djk </span>
    <textarea></textarea>
</div>

CSS

div {
    height: 20em;
    background-color: gray;
}
textarea {
    display: block;
    border:none;
}
span {
    padding:1em;
    display: inline-block;
}

JavaScript

document.getElementsByTagName('textarea')[0].style.height = (document.querySelector('div').offsetHeight-document.querySelector('span').offsetHeight-4)+'px'

alert((document.querySelector('div').offsetHeight-document.querySelector('span').offsetHeight)+'px')
alert(document.querySelector('div').offsetHeight)