how can I get the name of each argument in the arguments object in javascript

Question

In javascript we have the arguments object that is a not quite array that we can query.

How can I get the name of each argument?

For example if I want to know that the 3rd argument is called embedded for example, how would I discover this?

arguments[2].name == "embedded'

Obviously the above does not work.

Answer 1

I'm afraid that's not possible. Only the values themselves are passed:

function logArguments(){
    for(key in arguments)
        console.log(key, arguments[key]);
}
var someObject = {someProperty:false};

logArguments("1", 3, "Look at me I'm a string!", someObject);
// Returns:
// 0 1
// 1 3
// 2 "Look at me I'm a string!"
// 3 Object {someProperty: false}

So you can only get their array indexes.

You can however, use this for(key in arguments){} to supply as many arguments to a function as you'd want.

Answer 2

The arguments object is a list of parameters, it does not store the name of the arguments.

Some browsers let you use the toString method to get the code of a function:

function a(arg1){}
// undefined
a.toString()
// "function a(arg1){}"

If you need named parameters it's common to pass an object:

$.ajax({
  url: "test.html",
  cache: false
})

I'm not sure what you are trying to achieve... if you use positional arguments and the third argument is called "embedded" then the name of arguments[2] will always be "embedded". But while you know that when writing the code the name of the arguments aren't stored anywhere where you can conveniently access them.

Answer 3

something like this

function a() {
    var arr = Array.prototype.slice.call(arguments, 0, arguments.length);
    for (var aux in arr) {
        alert(aux + ":" + arguments[aux]);
    }
}

src: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Functions_and_function_scope/arguments