Uncaught TypeError: PromiseResolve called on non-object

[codersjj]

Consider the following code:

const values = [1, 2, 3]
const promises = values.map(Promise.resolve) // Uncaught TypeError: PromiseResolve called on non-object

This throws an error because Promise.resolve is being called incorrectly—it expects this to refer to the Promise constructor, but inside map, if we write the code as shown above, this becomes the global/window object or undefined(in strict mode).

When we use values.map(Promise.resolve), Promise.resolve is passed as a function reference, not as a method call on the Promise object. In JavaScript, methods lose their this binding when passed as callbacks.

Promise.resolve is designed to be called with the Promise constructor as its this context. When it's passed as a standalone function, it loses its this context (the Promise constructor), causing the internal PromiseResolve operation to attempt execution on undefined or the global/window object instead of on the Promise constructor.

However, I can't find any documentation about this "PromiseResolve called on non-object" TypeError. Could anyone point me to any existing documentation on this? If none exists, I'd be happy to create some. 😄

related docs:

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this#description:~:text=is%20non%2Dstrict.-,Callbacks,-When%20a%20function

reference links:

• https://stackoverflow.com/questions/45210122/why-cant-promise-resolve-be-called-as-a-function

[Josh-Cena]

This is sort of mentioned by:

Promise.resolve() is generic and supports subclassing, which means it can be called on subclasses of Promise, and the result will be a promise of the subclass type. To do so, the subclass's constructor must implement the same signature as the Promise() constructor — accepting a single executor function that can be called with the resolve and reject callbacks as parameters.

The this value must be a Promise subclass, so it cannot be undefined.