将参数传递给函数以返回链中的诺言

Question

I've a bunch of functions expecting parameters and returning promises, not sure how can I pass individual params to each one in the chain.

fs.readFile('./img/thumbnail.png', function(error, data) {
    module.create(body)
        .then(module.uploadImage) //expects collection.uploadImage(data);
        .then(module.requestInfo)
});

How can I make promises pass data to module.uploadImage as the parameter?

Answer 1

If the data is known at the time you enter the function, you can use .bind() :

fs.readFile('./img/thumbnail.png', function(error, data) {
    module.create(body)
        .then(module.uploadImage.bind(module, data))
        .then(module.requestInfo)
});

See the description of .bind() on MDN for more details.

---

You can of course, always just create your own wrapper function that lets you pass anything you want, including computed parameters:

fs.readFile('./img/thumbnail.png', function(error, data) {
    module.create(body).then(function() {
        return module.uploadImage(data);
    }).then(module.requestInfo)
});

PS Please don't ignore error checking on your fs.readFile() callback.

Answer 2

Use anonymous function:

fs.readFile('./img/thumbnail.png', function(error, data) {
module.create(body)
    .then(function(){ module.uploadImage(data); }) //expects collection.uploadImage(data);
    .then(module.requestInfo)
});