<!DOCTYPE html>
<title>Foo</title>
<div>Expected value: <b>test, a, b, c</b></div>
<div>Actual value: <b id="ret"></b></div>
<script>
var testdata = { test: 1, a: 2, b: 3, c: 4 };
var keys = Object.keys=Object.keys||function(o,k,r){r=[];for(k in o)r.hasOwnProperty.call(o,k)&&r.push(k);return r}
document.getElementById( "ret" ).innerHTML = keys(testdata);
</script>