Onchange is giving me "on" for the value of the event?

I have a function that fires when onchange happens. However event.target.value shows that “on” is the value. I am trying to have an object update with a checked mark show up when the box is checked.

<script type="text/javascript">

let lizt = {
            "learn": {
              "react": true,
              "python": false,
              "nodejs": false

            }
}


let lixxt = lizt["learn"];
let order = document.getElementById("order")

let status = lizt["learn"] ? '' : 'checked';

for (stuff in lixxt){

let status = !lixxt[stuff] ? '' : 'checked';
order.innerHTML += '<li>' + '<input type="checkbox"+ '  + status +  '>' + stuff + '</li>'

}


order.onchange = markit;

function markit(){
  let key = event.target.value;
  console.log(key)
}

hey

```<head>
```<title>JSON</title>
```</head>

```<body>
```<h1>hey</h1>
```<div id="div">
```  <ol id="order">

```  </ol>
```</div>

aaaannnnd. you sir just made my night better! Greetings Randell from Randall.