JSFiddle - React, Tailwind, and code Playground

HTML

<div id="app">
  <div style="height:100px;border:1px solid red;"></div>
  <codemirror id="code"></codemirror>
  <div style="height:100px;border:1px solid blue;"></div>
</div>

CSS

#app {
    display: flex;
    flex-flow: column nowrap;
    align-items: stretch;
}

#code {
    flex: 1;
    min-height: 0;
}

#code .CodeMirror {
    height: 100%;
}

html, body, #app {
    height: 100vh;
    width: 100vw;
    margin: 0;
}