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Reflect.has()

main Documentación oficial Licencia CC-BY-SA-2.5Descargado el 2026-08-02

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The Reflect.has() static method is like the in operator, but as a function.

{{InteractiveExample("JavaScript Demo: Reflect.has()")}}

```js interactive-example const object = { property1: 42, };

console.log(Reflect.has(object, "property1")); // Expected output: true

console.log(Reflect.has(object, "property2")); // Expected output: false

console.log(Reflect.has(object, "toString")); // Expected output: true

## Syntax

```js-nolint
Reflect.has(target, propertyKey)

Parameters#

  • target
  • : The target object in which to look for the property.
  • propertyKey
  • : The name of the property to check.

Return value#

A {{jsxref("Boolean")}} indicating whether or not the target has the property.

Exceptions#

  • {{jsxref("TypeError")}}
  • : Thrown if target is not an object.

Description#

Reflect.has() provides the reflective semantic of checking if a property is in an object. That is, Reflect.has(target, propertyKey) is semantically equivalent to:

propertyKey in target;

Reflect.has() invokes the [[HasProperty]] object internal method of target.

Examples#

Using Reflect.has()#

Reflect.has({ x: 0 }, "x"); // true
Reflect.has({ x: 0 }, "y"); // false

// returns true for properties in the prototype chain
Reflect.has({ x: 0 }, "toString");

// Proxy with .has() handler method
obj = new Proxy(
  {},
  {
    has(t, k) {
      return k.startsWith("door");
    },
  },
);
Reflect.has(obj, "doorbell"); // true
Reflect.has(obj, "dormitory"); // false

Reflect.has returns true for any inherited properties, like the in operator:

const a = { foo: 123 };
const b = { __proto__: a };
const c = { __proto__: b };
// The prototype chain is: c -> b -> a
Reflect.has(c, "foo"); // true

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#