JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="myiframe" name="myiframe"></iframe>

CSS

iframe#myiframe {
   white-space: pre-wrap;      /* CSS3 */   
   white-space: -moz-pre-wrap; /* Firefox */    
   white-space: -pre-wrap;     /* Opera <7 */   
   white-space: -o-pre-wrap;   /* Opera 7 */    
   word-wrap: break-word;      /* IE */    
}

JavaScript

window.onload = function () {
 myiframe.body.designMode = 'On';  
}