arity

> zero.length 0 > one.length 1 > two.length 2 Source A function can determine its own arity (length) like this: // For IE, and ES5 strict mode (named function) function foo(x, y, z) { return foo.length; // Will return 3 } // Otherwise function bar(x, y) { return arguments.callee.length; // Will return 2 }