TypeError: can't redefine non-configurable property "x"
The JavaScript exception "can't redefine non-configurable property" occurs when it was attempted to redefine a property, but that property is non-configurable.
Message
TypeError: Cannot redefine property: "x" (V8-based) TypeError: can't redefine non-configurable property "x" (Firefox) TypeError: Attempting to change value of a readonly property. (Safari)
Error type
What went wrong?
It was attempted to redefine a property, but that property is non-configurable. The
configurable
attribute controls whether the property can be deleted from
the object and whether its attributes (other than writable
) can be changed.
Usually, properties in an object created by an
object initializer are configurable. However, for example, when using
Object.defineProperty()
, the property isn't configurable by default.
Examples
Non-configurable properties created by Object.defineProperty
The Object.defineProperty()
creates non-configurable properties if you
haven't specified them as configurable.
js
const obj = Object.create({});
Object.defineProperty(obj, "foo", { value: "bar" });
Object.defineProperty(obj, "foo", { value: "baz" });
// TypeError: can't redefine non-configurable property "foo"
You will need to set the "foo" property to configurable, if you intend to redefine it later in the code.
js
const obj = Object.create({});
Object.defineProperty(obj, "foo", { value: "bar", configurable: true });
Object.defineProperty(obj, "foo", { value: "baz", configurable: true });