Baseline Widely available
The Reflect.has() static method is like the in operator, but as a function.
const object1 = {
property1: 42,
};
console.log(Reflect.has(object1, "property1"));
// Expected output: true
console.log(Reflect.has(object1, "property2"));
// Expected output: false
console.log(Reflect.has(object1, "toString"));
// Expected output: true
Reflect.has(target, propertyKey)
target
The target object in which to look for the property.
propertyKey
The name of the property to check.
A Boolean indicating whether or not the target has the property.
TypeError
Thrown if target is not an object.
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:
Reflect.has() invokes the [[HasProperty]] object internal method of target.
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
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4