js参数默认值

function functionName(parameterName = defaultValue) {
    // 函数体
}

// 基本数据类型的默认参数
function greet(name = 'World') {
    console.log(`Hello, ${name}!`);
}

greet(); // 输出: Hello, World!
greet('Alice'); // 输出: Hello, Alice!

// 对象类型的默认参数
function createPerson(firstName = 'John', lastName = 'Doe') {
    return { firstName, lastName };
}

console.log(createPerson()); // 输出: { firstName: 'John', lastName: 'Doe' }
console.log(createPerson('Jane')); // 输出: { firstName: 'Jane', lastName: 'Doe' }

// 函数类型的默认参数
function repeatMessage(message, times = 1) {
    for (let i = 0; i < times; i++) {
        console.log(message);
    }
}

repeatMessage('Hello'); // 输出: Hello
repeatMessage('Hello', 3); // 输出: Hello (3次)