According to the web worker MDN docs(https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Functions_and_classes_available_to_workers), Promise is not in the available list. But when I try to debug in worker file, and console log the self object, it has Promise inside. The Promise screenshot
I try to run new Promise() in web worker, and it works.I am confused why I can call Promise in web worker
The article you made reference to (Functions and classes available to Web Workers) starts with the definition of its scope:
...there are a variety of functions available from the DOM to workers. This article provides a list of those.
In other words, it covers the features from the Web API which are available to Web Workers.
Promise is not part of the Web API, but part of the ECMAScript language specification.
Although workers run in another global context, the ECMAScript language specification (since ES 2015) requires that the global context defines Promise.
In a related article, Using Web Workers, Mozilla Contributors write:
The worker context is represented by a
DedicatedWorkerGlobalScopeobject...
The linked article on DedicatedWorkerGlobalScope has:
Some additional global functions, namespaces objects, and constructors, not typically associated with the worker global scope, but available on it, are listed in the JavaScript Reference.
The linked JavaScript Reference article finally lists all built-is, including Promise.
