javaScript - pass object as function argument

I want to use an object as function argument. When I define an object outside fucntion and then pass it as an argument, it works fine:

var obj = {
  a: 0
}

function foo(obj){
  console.log(this.obj.a); 
}

foo() //0

But when I pass an object directly, it doesen't work:

function bar({a: 0}){
  console.log(this.arguments.a)
}
// Uncaught SyntaxError: Unexpected number

An object doesent seem to be a legal argument. How do I fix it?