setkey.js

function save_options() {
  var customapikey = document.getElementById('customapikey').value;
  if(document.getElementById('radioCustom').checked && customapikey !== '') {
  //use custom key
	chrome.storage.sync.set({
		customapikey: customapikey
	}, function() {
    // update status
		var status = document.getElementById('status');
		status.textContent = 'Options saved.';
		setTimeout(function() {
			status.textContent = '';
		}, 750);
	});
  }else if(document.getElementById('radioDefault').checked || customapikey === '') {
  //use default key
	chrome.storage.sync.remove('customapikey', function() {
		var status = document.getElementById('status');
		status.textContent = 'Options saved.';
		document.getElementById('radioDefault').checked = true;
		document.getElementById('customapikey').value = '';
		setTimeout(function() {
			status.textContent = '';
		}, 750);
	});
  }
}

function restore_options() {
	document.getElementById('save').addEventListener('click',
    save_options);
	
	chrome.storage.sync.get("customapikey", function(data) {
		if (typeof data['customapikey'] == 'undefined'){
			
		}else{
			document.getElementById('customapikey').value = data['customapikey'];
			document.getElementById('radioCustom').checked = true;
		}
	});
}

document.addEventListener('DOMContentLoaded', restore_options);