Reflect.has()
The static Reflect.has()
method works like the in
operator
as a function.
Syntax
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 Boolean
indicating whether or not the target
has the property.
Exceptions
Description
The Reflect.has
method allows you to check if a property is in an object.
It works like the in
operator
as a function.
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
Specification |
---|
ECMAScript Language Specification # sec-reflect.has |
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