1.形参初始值, 具有默认值的参数,一般位置要靠后(潜规则)
function add(a,b,c=10){ return a + b + c; } let resutl = add(1,2); //13
2. 与解构赋值结合
function connect ({host = "127.0.0.1",username,password, port}){ console.log(host); console.log(username); console.log(password); console.log(port); } connect({ username:'root', password:'root', port:'8080' })