console-panel | console panel within webpage to help in the following use

Promises are designed to store either a future result (the argument to res() above) or a future error (the argument to rej() above) but not both. It is therefore not valid to call both res() and rej() in a Promise body.

In this example, when trying to resolve the future values of a and b, the promise returned by Promise.all will call either the function passed to then() or the function passed to catch() based on the resolution or rejection of a or b.

Usually, it will call the function passed to then() with a list containing first values with which a and b resolved. If either promise rejects prior to resolving, however, the promise returned by Promise.all will call the function passed to .catch().

Since the a promise always resolves, and because the b promise resolves first, and does so with the value, car, Promise.all([a,b]) will resolve with a value containing car. It will not reject with the value bar because b resolved first.

Although the Promise implementation provided by your browser handles the double reject/resolve silently, do note that this could result in undefined behavior. For example, some implementations of Promise will throw an exception when used in this way.