Javascript Promise 问题，为什么 Chain 不起作用

Question

So this works

 new Promise(res => { console.log("1") res(res); }).then(res => { console.log("2") }).then(res => { console.log("3") })

But if I exclude the res(res), it will not chain. But it chains fine afterwards without any additional res().

Why is that, why does the first block matter if it has that res() and the subsequent blocks don't need it in order to chain onwards ?

Thanks.

Answer 1

It chains just fine without the call to res() in that the succeeding .then() handlers are chained onto the original promise.

But, the original promise will never be resolved so therefore, it will never call your .then() handlers. At some point, you have to resolve the promise if you want the .then() handlers to get called.