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.
TypeError: "x" is not a non-null object
Message
TypeError: Invalid descriptor for property {x} (Edge) TypeError: "x" is not a non-null object (Firefox) TypeError: Property description must be an object: "x" (Chrome) TypeError: Invalid value used in weak set (Chrome)
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 });
WeakMap
and WeakSet
objects require object keys
See also
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/No_non-null_object