聊聊JavaScript中的可选 (?.)操作符

console.log(user.homeaddress.country);

// 中国

console.log(user.officeaddress.country);

// throws error "Uncaught TypeError: Cannot read property 'country' of undefined"

console.log(user.officeaddress?.country);

// undefined

console.log(user.getFirstName());

console.log(user.getLastName());

// throws error "Uncaught TypeError: user.getLastName is not a function";

console.log(user.getLastName?.());

// "undefined"

console.log(user.hobbies[0].name);

// "敲代码"

console.log(user.hobbies[3].name);

// throws error "Uncaught TypeError: Cannot read property 'name' of undefined"

console.log(user.dislikes?.[0]?.name);

// "undefined"

const country = user.officeaddress?.country;

console.log(country);

// undefined

const country = user.officeaddress?.country ?? "中国";

console.log(country);

// 中国