如何在承诺链中间传递论点？

Question

I have a promise chain as follows:

...

const id = "someId";

function1(id)
    .then(function2)
    .then(function3(id))
    .then(function4)
    .then(result => {
        res.status(200).send(result);
    })
    .catch(error => {
        res.status(500).end();
    });

...

Where function1, function2, function3, and function4 need to be called in order and each uses the result returned from the previous. The problem I am running into is that function3 requires the id parameter, but whenever I set it as shown above then the result from function3 is not passed to function4. How do I pass the id parameter to function3 and pass the result from function3 to function4?

Answer 1

You're calling function3 directly, without respecting the chain.

You have to do it this way:

.then(() => function3(id))
// or if you need the response from `function2`
.then(res => function3(id, res))

Or an alternative is to use .bind

.then(function3.bind(null, id)) // instead of null you can pass some context

Otherwise function3 will need to return a function, that will be used by .then handler when function2 resolves.