Promise patterns in node.js

promises_in_nodejs.txt

After reading a lot of pages about Promises, this page finally started making sense for me. It's a looong read and quite advanced but there are some good nuggets that help clarify things:

        https://pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html

#. Always end a promise compose chain with

        catch(console.log.bind(console))

#. Inside a .then() ALWAYS RETURN OR THROW never let it be 'undefined'

        return another promise
        return a synchronous value (or undefined)
        throw a synchronous error

#. When composing, name your promises:

        var x = request({ method: 'GET', url: 'icanhazip.com' })
        x.then(response => { dosomething(response); return this })
        x.catch(console.log.bind(console))


# To indicate that order of op is not significant, compose with Promise.all:

        var x = request({ method: 'GET', url: 'icanhazip.com' })
        var y = request({ method: 'GET', url: 'helloacm.com/api/fortune' })
        var z = Promise.all([x, y])
        z.then(response => { dosomething(response); return this })
        z.catch(console.log.bind(console))

# This shows how to splice non-promise stuff into a promise pipe, thanks Fermi:

```
const Promise = require('bluebird')
var options = ['. abcd. ']

function inner(options) {return options}

function transform(options) {return options.trim()}

function wrapper(options) {
  return new Promise (
    resolve => { return resolve() }
  )
  .then( () => inner(options) )
  .then( data => transform(data))
}

wrapper(options)
.then(response => console.log('done: ' + response))
```