node.js 非空判断

function printName(name) {
    if (name !== null && name !== undefined) {
        console.log(`Name: ${name}`);
    } else {
        console.log("Name is not provided.");
    }
}

printName("Alice"); // 输出: Name: Alice
printName(null);     // 输出: Name is not provided.

function printUser(user) {
    if (user && typeof user === 'object' && !Array.isArray(user)) {
        console.log(`User: ${JSON.stringify(user)}`);
    } else {
        console.log("Invalid user object.");
    }
}

printUser({ name: "Bob", age: 30 }); // 输出: User: {"name":"Bob","age":30}
printUser([]);                       // 输出: Invalid user object.

const user = {
    profile: {
        name: "Charlie"
    }
};

console.log(user?.profile?.name); // 输出: Charlie
console.log(user?.address?.city); // 输出: undefined，不会抛出错误

function getUserName(user) {
    return user ? user.name : "Unknown";
}

console.log(getUserName({ name: "Dave" })); // 输出: Dave
console.log(getUserName(null));            // 输出: Unknown

const numbers = [1, 2, null, 4, undefined, 6];
const filteredNumbers = numbers.filter(num => num !== null && num !== undefined);
console.log(filteredNumbers); // 输出: [1, 2, 4, 6]