JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://rawgithub.com/jrideout/melt.js/master/melt.js"></script>
Origional:
<pre id="old">
[{"Pass": "10", "Fail": "20", "Untested": "40"},
 {"Pass": "20", "Fail": "40", "Untested": "50"},
 {"Pass": "20", "Fail": "40", "Untested": "50", "extra": "2"},
 {"Pass": "30", "Fail": "50", "Untested": "60"}]
</pre>
Melted:
<pre id="new">
</pre>

CSS

pre {
    border: 1px dashed;
    padding: 4px;
    white-space: pre-wrap; 
}

JavaScript

var old = document.getElementById("old").textContent,
    old = JSON.parse(old);

var moltenObject = melt(old);

document.getElementById("new").textContent = JSON.stringify(moltenObject,null);