Flexible Flow Async

// This demo supports flowing together async and non async methods // If nothing is async, it *stays sync* // also handles arrays of promises (e.g. from _.map) and objects of promises (e.g. from _.mapValues) // does NOT handle promises for keys let _ = require('lodash/fp') let Promise = require('bluebird') let promisedProps = Promise.props || (async x => _.zipObject(_.keys(x), await Promise.all(_.values(x)))) let isPromiseArray = _.overEvery([_.some('then'), _.isArray]) let isPromiseObject = _.overEvery([_.some('then'), _.isPlainObject]) // calls then conditionally, allowing flow to be used synchronously, too let callOnAsync = (value, f) => (value.then ? value.then(f) : f(value)) let asyncCall = (prop, f) => { if (_.some('then', prop)) { if (_.isArray(prop)) return Promise.all(prop).then(f) if (_.isPlainObject(prop)) return promisedProps(prop).then(f) } if (prop.then) return prop.then(f) return f(prop) } let flowWith = call => (fn0, ...fns) => (...x) => [...fns, x => x].reduce(call, fn0(...x)) let flowAsync = flowWith(asyncCall) let slowDouble = async x => { await Promise.delay(10) return x * 2 } let testMidAsync = flowAsync(_.get('a'), slowDouble, x => x * 3) console.log(await testMidAsync({ a: 4 })) let testSync = flowAsync(_.get('a'), x => x + 2) console.log(testSync({ a: 1 })) let testArrayAsync = flowAsync(_.map(slowDouble), _.map(x => x * 2)) console.log(await testArrayAsync([1, 2])) // let testAsyncObj = flowAsync(_.mapValues(slowDouble), _.mapKeys(slowDouble)) // console.log(await testAsyncObj({ a:1 }))