Typescript有条件地需要参数

function greet(name: string, age?: number) {
  if (age) {
    console.log(`Hello ${name}, you are ${age} years old.`);
  } else {
    console.log(`Hello ${name}.`);
  }
}

greet("Alice"); // 输出：Hello Alice.
greet("Bob", 25); // 输出：Hello Bob, you are 25 years old.

function greet(name: string, age: number = 18) {
  console.log(`Hello ${name}, you are ${age} years old.`);
}

greet("Alice"); // 输出：Hello Alice, you are 18 years old.
greet("Bob", 25); // 输出：Hello Bob, you are 25 years old.