Reflect.ownKeys()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2016.
The Reflect.ownKeys()
static method returns an array of the target
object's own property keys.
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Syntax
Reflect.ownKeys(target)
Parameters
target
-
The target object from which to get the own keys.
Return value
An Array
of the target
object's own property keys, including strings and symbols. For most objects, the array will be in the order of:
- Non-negative integer indexes in increasing numeric order (but as strings)
- Other string keys in the order of property creation
- Symbol keys in the order of property creation.
Exceptions
TypeError
-
Thrown if
target
is not an object.
Description
Reflect.ownKeys()
provides the reflective semantic of retrieving all property keys of an object. It is the only way to get all own properties – enumerable and not enumerable, strings and symbols — in one call, without extra filtering logic. For example, Object.getOwnPropertyNames()
takes the return value of Reflect.ownKeys()
and filters to only string values, while Object.getOwnPropertySymbols()
filters to only symbol values. Because normal objects implement [[OwnPropertyKeys]]
to return all string keys before symbol keys, Reflect.ownKeys(target)
is usually equivalent to Object.getOwnPropertyNames(target).concat(Object.getOwnPropertySymbols(target))
. However, if the object has a custom [[OwnPropertyKeys]]
method (such as through a proxy's ownKeys
handler), the order of the keys may be different.
Reflect.ownKeys()
invokes the [[OwnPropertyKeys]]
object internal method of target
.
Examples
Using Reflect.ownKeys()
Reflect.ownKeys({ z: 3, y: 2, x: 1 }); // [ "z", "y", "x" ]
Reflect.ownKeys([]); // ["length"]
const sym = Symbol.for("comet");
const sym2 = Symbol.for("meteor");
const obj = {
[sym]: 0,
str: 0,
773: 0,
0: 0,
[sym2]: 0,
"-1": 0,
8: 0,
"second str": 0,
};
Reflect.ownKeys(obj);
// [ "0", "8", "773", "str", "-1", "second str", Symbol(comet), Symbol(meteor) ]
// Indexes in numeric order,
// strings in insertion order,
// symbols in insertion order
Specifications
Specification |
---|
ECMAScript Language Specification # sec-reflect.ownkeys |
Browser compatibility
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