Summary
An Array
-like object corresponding to the arguments passed to a function.
Variable of the function scope | |
---|---|
Implemented in | JavaScript 1.1 |
ECMAScript Version | ECMA-262 |
Description
The arguments
object is a local variable available within all functions; arguments
as a property of Function
can no longer be used.
You can refer to a function's arguments within the function by using the arguments
object. This object contains an entry for each argument passed to the function, the first entry's index starting at 0. For example, if a function is passed three arguments, you can refer to the argument as follows:
arguments[0]
arguments[1]
arguments[2]
The arguments can also be set:
arguments[1] = 'new value';
arguments[n]
cannot be set if n
is greater than the number of formal or actual parameters. This has been fixed in the engine for JavaScript 1.6.The arguments
object is not an Array
. It is similar to an Array
, but does not have any Array
properties except length
. For example, it does not have the pop
method. However it can be converted to a real Array
:
var args = Array.prototype.slice.call(arguments);
If Array generics are available, one can use the following instead:
var args = Array.slice(arguments);
The arguments
object is available only within a function body. Attempting to access the arguments
object outside a function declaration results in an error.
You can use the arguments
object if you call a function with more arguments than it is formally declared to accept. This technique is useful for functions that can be passed a variable number of arguments. You can use arguments.length
to determine the number of arguments passed to the function, and then process each argument by using the arguments
object. (To determine the number of arguments declared when a function was defined, use the Function.length
property.)
Properties
-
arguments.callee
- Reference to the currently executing function.
-
arguments.caller
Obsolete - Reference to the function that invoked the currently executing function.
-
arguments.length
- Reference to the number of arguments passed to the function.
Examples
Example: Defining a function that concatenates several strings
This example defines a function that concatenates several strings. The only formal argument for the function is a string that specifies the characters that separate the items to concatenate. The function is defined as follows:
function myConcat(separator) { var result = ""; // iterate through non-separator arguments for (var i = 1; i < arguments.length; i++) { result += arguments[i] + separator; } return result; }
You can pass any number of arguments to this function, and it creates a list using each argument as an item in the list.
// returns "red, orange, blue, " myConcat(", ", "red", "orange", "blue"); // returns "elephant; giraffe; lion; cheetah; " myConcat("; ", "elephant", "giraffe", "lion", "cheetah"); // returns "sage. basil. oregano. pepper. parsley. " myConcat(". ", "sage", "basil", "oregano", "pepper", "parsley");
Example: Defining a function that creates HTML lists
This example defines a function that creates a string containing HTML for a list. The only formal argument for the function is a string that is "u
" if the list is to be unordered (bulleted), or "o
" if the list is to be ordered (numbered). The function is defined as follows:
function list(type) { var result = "<" + type + "l>"; // iterate through non-type arguments for (var i = 1; i < arguments.length; i++) { result += "<li>" + arguments[i] + "</li>"; } result += "</" + type + "l>"; // end list return result; }
You can pass any number of arguments to this function, and it adds each argument as an item to a list of the type indicated. For example:
var listHTML = list("u", "One", "Two", "Three"); /* listHTML is: "<ul><li>One</li><li>Two</li><li>Three</li></ul>" */