How to tell if a promise is resolved? [duplicate]

Question

Suppose some code does

// promise.js let p = new Promise(() => { /* ... */ }) export default p 

where Promise is an ES6 Promise. Suppose some other code has a reference only to p. How can that code tell if p is resolved or not?

// other.js import p from './promise.js' // console.log('p is resolved?', ______) 

Is there something we can fill in the blank with that would show true or false depending on whether the promise is resolved or not?

Answer 1

Quoting the MDN documentation:

By design, the instant state and value of a promise cannot be inspected synchronously from code, without calling the then() method.

So, you need to call the .then method.

Answer 2

The ES6 Promise constructor does not have a property that can tell you the state of the promise. You need to do something like this:

import p from './promise.js' var isResolved = false; p.then(function() {   isResolved = true; });  // ... At some point in the future. console.log('p is resolved?', isResolved); 

There is an internal property called PromiseState but you can't access it. Here is the spec.