Function.prototype.arguments
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
Note: The arguments
property of Function
objects is deprecated. The recommended way to access the arguments
object is to refer to the variable arguments
available within functions.
The arguments
accessor property of Function
instances returns the arguments passed to this function. For strict, arrow, async, and generator functions, accessing the arguments
property throws a TypeError
.
Description
The value of arguments
is an array-like object corresponding to the arguments passed to a function.
In the case of recursion, i.e. if function f
appears several times on the call stack, the value of f.arguments
represents the arguments corresponding to the most recent invocation of the function.
The value of the arguments
property is normally null
if there is no outstanding invocation of the function in progress (that is, the function has been called but has not yet returned).
Note that the only behavior specified by the ECMAScript specification is that Function.prototype
has an initial arguments
accessor that unconditionally throws a TypeError
for any get
or set
request (known as a "poison pill accessor"), and that implementations are not allowed to change this semantic for any function except non-strict plain functions. The actual behavior of the arguments
property, if it's anything other than throwing an error, is implementation-defined. For example, Chrome defines it as an own data property, while Firefox and Safari extend the initial poison-pill Function.prototype.arguments
accessor to specially handle this
values that are non-strict functions.
(function f() {
if (Object.hasOwn(f, "arguments")) {
console.log(
"arguments is an own property with descriptor",
Object.getOwnPropertyDescriptor(f, "arguments"),
);
} else {
console.log(
"f doesn't have an own property named arguments. Trying to get f.[[Prototype]].arguments",
);
console.log(
Object.getOwnPropertyDescriptor(
Object.getPrototypeOf(f),
"arguments",
).get.call(f),
);
}
})();
// In Chrome:
// arguments is an own property with descriptor {value: Arguments(0), writable: false, enumerable: false, configurable: false}
// In Firefox:
// f doesn't have an own property named arguments. Trying to get f.[[Prototype]].arguments
// Arguments { … }
Examples
Using the arguments property
function f(n) {
g(n - 1);
}
function g(n) {
console.log(`before: ${g.arguments[0]}`);
if (n > 0) {
f(n);
}
console.log(`after: ${g.arguments[0]}`);
}
f(2);
console.log(`returned: ${g.arguments}`);
// Logs:
// before: 1
// before: 0
// after: 0
// after: 1
// returned: null
Specifications
Not part of any standard.
Browser compatibility
BCD tables only load in the browser