url 解构赋值

function parseProtocol(url) {
var parsedURL = /^(\w+)://([/]+)/(.*)$/.exec(url);
if (!parsedURL) {
return false;
}
console.log(parsedURL); // ["https://developer.mozilla.org/en-US/Web/JavaScript", "https", "developer.mozilla.org", "en-US/Web/JavaScript"]

var [, protocol, fullhost, fullpath] = parsedURL;
return protocol;
}

console.log(parseProtocol('https://developer.mozilla.org/en-US/Web/JavaScript')); // "https"