get function arguments count from external scope

Question

Is it possible to get function arguments count from external scope?

var foo = function(a,b,c) {
}

alert(foo.arguments.length); // how to do it? possible?

Answer 1

You want Function.length:

function test(a, b, c) {
  // code
}

console.log(test.length); // 3

BTW, the number of expected arguments of a function is called the arity. There used to be a method called Function.arity but was deprecated in favour of Function.length.

Answer 2

try foo.length. It gives no of parameters defined in function definition.