let sndInput = document.querySelector('input[name="sndfile"]');
let sndTest = document.querySelector('audio[name="sndtest"]');

sndInput.onchange = function(event) {
	var reader = new FileReader();
	reader.readAsDataURL(sndInput.files[0]);
	reader.onload = function () {
		sndTest.src = reader.result;
		browser.storage.local.set({sound: reader.result});
	};
	reader.onerror = function() {
		window.alert(reader.error);
	}
	sndInput.value = "";
}

browser.storage.local.get({sound: null}, function({sound}) {
	sndTest.src = sound;
});