revise a note of promise then.

[zjffun]

I'm not sure if I misunderstood this note. According to:

https://tc39.es/ecma262/#sec-performpromisethen

Else if promise.[[PromiseState]] is fulfilled, then ---Let value be promise.[[PromiseResult]]. ---Let fulfillJob be NewPromiseReactionJob(fulfillReaction, value).

https://tc39.es/ecma262/#sec-newpromisereactionjob

If handler is undefined, then ---If type is Fulfill, let handlerResult be NormalCompletion(argument).

if you don't provide then() a non-function, the next then() resolve function will passed the value the current resolve function passed.

eg:

> Promise.resolve(42).then(24).then(d => console.log(d))
// 42

> Promise.resolve(42).then({}, ()=>{}).then(d => console.log(d))
// 42

> Promise.resolve(42).then().then(d => console.log(d))
// 42