Edit in JSFiddle

const data = {
	"dcids": [
		"country/PLW"
	]
}
const request = new XMLHttpRequest();
request.open("POST", "https://api.datacommons.org/place/stat-vars", false /* async */ );
request.send(JSON.stringify(data));

if (request.status == 200) {
  let result = JSON.parse(request.responseText)["places"]["country/PLW"]["statVars"];
  console.log(result);
  
  for (let i = 0; i < result.length; i+=1) {
    let resultName = result[i];
    document.write(resultName + "<br>");
  }
  
  
} else {
  console.log("There was an error fetching data.");
}

Statistical variables available for the country of Palau: <div id="country/PLW">
</div>