how to call the functions that are object members?

I have want to call the function that is a object attribute. For example consider the code

var obj={
  a:"One",
  b:"two",
  c:'three',
  d:function f(){
    console.log("Hello World");
  }
}

I want to call the function f. How would I do that? I tried to google, but I am unable to find it anywhere, Maybe I am phrasing the question wrong wrong.