函数的参数是存在于Typescript类型中的属性

function greet(name: string) {
  console.log("Hello, " + name);
}

greet("Alice"); // 输出：Hello, Alice

function greet(name?: string) {
  if (name) {
    console.log("Hello, " + name);
  } else {
    console.log("Hello, stranger");
  }
}

greet("Alice"); // 输出：Hello, Alice
greet(); // 输出：Hello, stranger

function greet(name: string = "stranger") {
  console.log("Hello, " + name);
}

greet("Alice"); // 输出：Hello, Alice
greet(); // 输出：Hello, stranger

type GreetFunction = (name: string) => void;

const greet: GreetFunction = (name) => {
  console.log("Hello, " + name);
}

greet("Alice"); // 输出：Hello, Alice