lodash-fp-composition

keep the darkside away: practical functional mixins for lodash/fp to make code more readable, maintainable & composable

Warning: Experimental

Philosophy

1. functional programming in javascript has 2 categories: the good stuff..and there's the other stuff :)
2. _.flow (=reversed compose) & _.trigger saves us from writing lots of functions & if/else statements
3. mixing functions & promises should be hasslefree

So..what could code look like with this library?

engine                   = {}
engine.getOrCreateUser   = _.flow( 
                               _.trigger( console.dir ), 
                               _.either( engine.getUser, engine.createUser ), 
                               _.trigger( 'address.verified', (v) => console.log("verified:"+v) ), 
                               _.trigger( _.set('meta.lastlogin', Date.now ) ),  
                               _.when( _.get('id'),      (dbUser) => console.log("loaded user:"+dbUser.id) ), 
                               _.when( _.getno('id') ), () => throw 'could not load user' )
                           )
                           .catch( console.error )

engine.getOrCreateUser({email:"[e-mail]"})
.then( (user) => console.dir(user) )

Instead of:

engine                   = {}
engine.getOrCreateUser   = function(user){
    return new Promise( (resolve, reject) => {
        console.dir(user)
        engine.getUser(user)
        .then( (dbUser) => {
            if( !dbUser ) return engine.createUser(user)
            else return dbUser
        })
        .then( (dbUser) => {
            if( dbUser ){
              if( dbUser.address && dbUser.address.verified ) console.log("verified:"+v)
              console.log("user ok") 
              if( !dbUser.meta ) dbUser.meta = {}
              dbUser.lastlogin = Date.now()
              if( dbUser.id ) console.log("loaded user: "+dbUser.id)
              else throw 'could not load user'
            }
        })
        .catch( console.error )
    })
}

engine.getOrCreateUser({email:"[e-mail]"})
.then( (user) => console.dir(user) )

---

Function Reference

_.flow( mixed_arguments_of_promises_and_functions, ... )

Improved version of _.flow, which also supports automatic resolving of promises. Note: modifies output.

example: a = _.flow( new Promise(.....), _.trigger(alert), Object.keys ) a({foo:1, bar:2})

  input:{foo:1,bar:2} --->  promise --+--> Object.keys(input) ) 
                                      |
                                      +--> alert(input)
  output:['foo','bar'] 

_.trigger(fn)

trigger simply executes a function OR promise, but forwards original input as output. this comes in handy when you don't want to break a flow/chain

example: _.flow( _.trigger( alert ), _.trigger(console.dir) )({foo:"bar"})

_.either(a, b)

this will execute function b only when function a returns false/null/undefined

example: _.either(getUserByEmail,createUserEmail)("[e-mail]")

_.getno(path)

this is the opposite of _.get

example: var a = _.getno( 'foo.bar' ) a({foo:1}) // returns true

_.maybe(fn)

this will execute function fn only when there's input. this comes in handy when its unsure whether the previous function was succesful in a chain/flow/composed function.(){}

example: .flow( getOrCreateUser, maybe(.log("user ok")) )

_.when(f, g)

hipster if statement, only execute function g when function f does not return null/false/undefined

example: _.when( _.isString, console.log )("foo")

_.lensOver(path, fn)

lens over allows i/o for a nested property

example: var updateBar = _.flow( -> 123, _.log ) _.lensOver( "foo.bar", updateBar )({foo:{bar:0}}) // sets 'foo.bar' to 123 (and prints in console)

_.template_es6(es6_template)

simple es6 templates for in the browser

example: _.template_es6('${foo}', {foo:"bar"}) // outputs 'bar'

_.prefix(prefix, fn)

simple way to prefix a function which outputs a string

example: _.error = _.prefix("error: ", _.log)

_.postfix(postfix, fn)

simple way to postfix a function which outputs a string

example: _.flow( _.get('.length'), _.prefix("items", _.log) )([1, 2, 3])

_.log(str)

simple log function (which forwards input to output)

example: _.flow( doFoo, _log, doBar )({input:"foo"})

_.error(str)

simple error function (which forwards input to output)

example: _.when( !hasFoo, _.prefix("something went wrong:", _error ) )({input:"foo"})

_.mapAsync(arr, done, cb)

calls cb(data, next) for each element in arr, and continues loop based on next()-calls (last element propagates done()). Perfect to iterate over an array synchronously, while performing async operations inbetween the elements.

example: _.mapAsync([1, 2, 3], alert, (data, next) => next() )