方法一 使用多个形参，并为每个形参设置默认值
function introduce(name="zhansan",country="China",age=18){
return `My name is ${name}. I am come from ${country}. I am 18 years old..`;
}
console.log(introduce("lisi")); //My name is lisi. I am come from China. I am 18 years old.
console.log(introduce("wangwu","China",20)); //My name is wangwu. I am come from China. I am 20 years old.
- 缺点：当age改变，而country没改变时，依然需要传递country的值
方法二 传入一个对象，为每个属性设置默认值
function introduce({name="zhansan",country="China",age=18}){
return `My name is ${name}. I am come from ${country}. I am ${age} years old.`;
};
console.log(introduce({name:"lisi"})); //My name is lisi. I am come from China. I am 18 years old.
console.log(introduce({name:"wangwu",age:20})); //My name is wangwu. I am come from China. I am 20 years old.
使用这种方法我们只需传入改变的值，其他值都会使用默认值
