通过解决，拒绝外部承诺到内部承诺

Question

I have a basic promise code which works as below

 new Promise(function(resolve, reject) { new Promise(function(resolveInner, rejectInner) { // do something resolveInner('resolved inner promise') }).then(function(msg) { console.log(msg); // do something resolve("resolved from inner") }).catch(function(msg) { console.log('error' + msg) }) }).then(function(msg) { console.log(msg) }) 

I am trying to refactor and modularize the code by bringing the innerResolve function outside like below. This errors out as 'resolve' is undefined

 new Promise(function(resolve, reject) { new Promise(function(resolveInner, rejectInner) { // do something resolveInner('resolved inner promise') }).then(innerResolve) // externalized here !!!! .catch(function(msg) { console.log('error' + msg) }) }).then(function(msg) { console.log(msg) }) function innerResolve(msg) { console.log(msg); // do something resolve("resolved from inner") } 

How do I bring outer Promise resolve to innerResolve function?

One solution is to create a global variable which could be set to outer promise resolve for example.

 var _resolve; new Promise(function(resolve, reject) { _resolve = resolve new Promise(function(resolveInner, rejectInner) { // do something resolveInner('resolved inner promise') }).then(innerResolve).catch(function(msg) { console.log('error' + msg) }) }).then(function(msg) { console.log(msg) }) function innerResolve(msg) { console.log(msg); // do something _resolve("resolved from inner") } 

Is there a better approach without global variables?

Answer 1

Your situation seems really convoluted, so you might want to re-evaluate why you need to do this at all, but if it is simply experimenting, you can solve this without globals, by passing the appropriate resolver to a function generator. For example:

 const innerResolve = resolver => msg => { console.log(msg); // do something resolver("resolved from inner") } new Promise(function(resolve, reject) { new Promise(function(resolveInner, rejectInner) { // do something resolveInner('resolved inner promise') }).then(innerResolve(resolve)).catch(function(msg) { console.log('error' + msg) }) }).then(function(msg) { console.log(msg) })