JSFiddle - React, Tailwind, and code Playground

HTML

<div id='results'></div>

JavaScript

var strs = 
    [ 'thisStringIsGood'
    , 'somethingLikeThis'  
    ,  'a123CapsHere345AndHEREButNOT678Here90End'
    , '123CapsHere345AndHEREButNOT678Here90e'
    ];

function capSplit(str){
   return str.replace
      ( /(^[a-z]+)|[0-9]+|[A-Z][a-z]+|[A-Z]+(?=[A-Z][a-z]|[0-9])/g
      , function(match, first){ 
          if (first) match = match[0].toUpperCase() + match.substr(1);
          return match + ' ';
          }
       )
   }
for (var str in strs) 
    if (strs.hasOwnProperty(str))     
       document.getElementById('results').innerHTML += capSplit(strs[str]+"<br>");