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Showing content from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/No_non-null_object below:

TypeError: "x" is not a non-null object - JavaScript

TypeError: "x" is not a non-null object

The JavaScript exception "is not a non-null object" occurs when an object is expected somewhere and wasn't provided. null is not an object and won't work.

Message

TypeError: Property description must be an object: x (V8-based)
TypeError: Property descriptor must be an object, got "x" (Firefox)
TypeError: Property description must be an object. (Safari)

Error type What went wrong?

An object is expected somewhere and wasn't provided. null is not an object and won't work. You must provide a proper object in the given situation.

Examples Property descriptor expected

When methods like Object.create() or Object.defineProperty() and Object.defineProperties() are used, the optional descriptor parameter expects a property descriptor object. Providing no object (like just a number), will throw an error:

Object.defineProperty({}, "key", 1);
// TypeError: 1 is not a non-null object

Object.defineProperty({}, "key", null);
// TypeError: null is not a non-null object

A valid property descriptor object might look like this:

Object.defineProperty({}, "key", { value: "foo", writable: false });