function.arguments

[ljharb]

Should it return a frozen array every time it's evaluated? Is there any use case for which mutability of this array would be desired?

[ExE-Boss]

Arguably, it should always return the same mutable array for the current environment to match how the arguments object is mutable.

[ExE-Boss]

I also consider function.arguments to be equivalent to capturing all arguments using the ... rest operator, eg.:

const foo = (bar, baz = 123) => {
	return {
		bar,
		baz,
		arguments: function.arguments,
	};
};

Is equivalent to the following ES2015 transpiled code:

const foo = (..._functionArguments) => {
	var { 0: bar, 1: baz = 123 } = _functionArguments;
	return {
		bar,
		baz,
		arguments: _functionArguments;
	};
};
Object.defineProperty(foo, "length", { value: 1, configurable: true });

Or transpiled to ES5:

var foo = function (bar) {
	var _functionArguments = [];
	for (var i = 0, length = arguments.length; i < length; i++) {
		_functionArguments[i] = arguments[i];
	}

	var baz = _functionArguments[1];
	if (baz === undefined) {
		baz = 123;
	}

	return {
		bar,
		baz,
		arguments: _functionArguments;
	};
}