How would I know which button caused this function to run? Specifically, if I want to set the value of the function to be equivalent to the value of the button?

```
var foo_button = document.getElementById("foo_button");
var bar_button = document.getElementById("bar_button");
foo_button.onclick = foo_or_bar;
bar_button.onclick = foo_or_bar;

```

Then in a function later on:

```
function foo_or_bar(){

    //this should return the value of the button that was pressed (in this case "foo" 
    //or "bar"
    return button_that_sent_me;

}

```

Is there a way I can detect the value of which button caused this to occur?