CODEWITHSUNDEEP
javascriptnode.js
Learner
Learner

Reputation: 21425

What properties are supported by arguments object

I was asked this question in an interview on NodeJS,

What are the properties supported by arguments object.

a) caller
b) callee
c) length
d) All

When I googled then I found that all the 3 properties are present for an argument object.

But if I try to test this with a sample program I see that only Length property is present.

Here is my sample program:

var events = 'HelloWorld'

abc(events);
function abc(args) {
    console.log(args.charAt(1))   
    console.log(args.callee);
    console.log(args.caller);
    console.log(args.length);
}

Here is the output:

e
undefined
undefined
10

So based on above output only length is the valid property, but based on above all 3 are valid properties. So what is the correct answer for this?

Upvotes: 2

Views: 793

Answers (1)

Bucket
Bucket

Reputation: 7521

Your scoped variable args and the local variable Function.arguments are two very different things. In your function abc(args), args is the scoped variable that will be whatever you pass into its invocation.

arguments, however, is a local array-like variable that is accessible inside each function call, and corresponds with the values passed into a function. For example:

function foo(args) {
    console.log(args);
    console.log(arguments[0]);
    console.log(arguments[1]);
    console.log(arguments[2]);
}

foo("bar", "baz", 123, 456);

This will output:

> "bar"
> "bar"
> "baz"
> 123

Even though this function only takes one argument, args, the local variable arguments is still present, and it represents all arguments passed into this function. That way we can still find the value of the second, third, and fourth arguments even though they weren't declared as part of the function's scope.

The issue you're seeing is that you are trying to access properties of Function.arguments in your scoped variable args, when the two are simply different variables altogether. If you want to access those properties, reference arguments instead:

var events = 'HelloWorld'
abc(events);

function abc(args) { 
    console.log(args.charAt(1));   
    console.log(arguments.callee);
    // console.log(arguments.caller); //DEPRECATED
    console.log(arguments.length);
}

Upvotes: 5

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