Section 24.5. Arguments.length: the number of arguments passed to a function

24.5. Arguments.length: the number of arguments passed to a function ECMAScript v1 24.5.1. Synopsis arguments.length 24.5.2. Description The length property of the Arguments object specifies the number of arguments passed to the current function. This property is defined only within a function body. Note that this property specifies the number of arguments actually passed, not the number expected. See Function.length for the number of declared arguments. Note also that this property does not have any of the special behavior of the Array.length property. 24.5.3. Example // Use an Arguments object to check that correct # of args were passed function check(args) { var actual = args.length; // The actual number of arguments var expected = args.callee.length; // The expected number of arguments if (actual != expected) { // Throw exception if they don't match throw new Error("Wrong number of arguments: expected: " + expected + "; actually passed " + actual); } } // A function that demonstrates how to use the function above function f(x, y, z) { check(arguments); // Check for correct number of arguments return x + y + z; // Now do the rest of the function normally } 24.5.4. See Also Array.length, Function.length