ES6 default values not available in function.arguments?

Question

If I have this ES6 function declaration and invocation:

function myFunction (arg1, arg2 = "bob") {
  console.log("arguments", arguments);
}

myFunction(1);

...the console.log() statement shows only one argument with a value of "1". "bob" is nowhere to be seen. Is this expected and/or desired behavior? I would expect that default values would be available in the arguments object. If not, is there a way to dynamically get all arguments + defaults in some other manner?

Thanks in advance!

Answer 1

Yes, this is expected and desired. The arguments object is a list of the values that were passed into the function, nothing else.

It is not implicily linked to the parameter variables (that get assigned the default values), like it was in sloppy mode.

Is there a way to dynamically get all arguments + defaults in some other manner?

No. What parameters you have and whether they have default initialisers is static, you don't need to do anything here dynamically. You can do Object.assign([], arguments, [arg1, arg2]) for your example function.