Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

Availability

JavaScript 1.1; JScript 2; ECMAScript v1

Synopsis

arguments.length

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.

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
}

See Also

Array.length, Function.length