Extracting Promise Chain to an external function

March 19, 2022

So Promises make everything so much cleaner and all but how do I extrapolate the end of a promise chain to an external function?

For example:

SomePromise.then(result => {
    // do stuff here
}).catch(err => {
    // do more stuff here
})

SomePromise2.then(result => {
    // do stuff here
}).catch(err => {
    // do more stuff here
})

SomePromise3.then(result => {
    // do stuff here
}).catch(err => {
    // do more stuff here
})

Somehow, I’d like to extract the then and catch so that I can pass a function into the then like such:

SomePromise.then(handler);
SomePromise2.then(handler);
SomePromise3.then(handler);

I suppose I could extract the entire Promise into a function and pass parameters to and from there but that feels a bit clunky. Any elegant solutions?

Edit: I should elaborate that I’m focusing on the catch part. Imagine multiple different queries with identical data-parsers and error handlers.

Edit 2: In hindsight I realize now that I could just extrapolate

handler = () => {}
errorHandler = () => {}

Promise.then(handler)
       .catch(errorHandler)

but the

>Solution :

let p1=Promise.resolve(1);
function handler(data){console.log(data)};
function errorHandler(error){console.log(error)};
p1.then(handler,errorHandler);

Multiple things here, your code you are expecting is:

SomePromise.then(handler);

However it should be in actual as

function handler(data){};
SomePromise.then((data)=>handler(data));