asynchronous promise-like function sequencing for dummies (like me)


asynchronous promise-like function sequencing for dummies (like me)

this is very much a 0.x project. I write examples instead of tests, I document features I'm still in the process of implementing (and really, I only document at all as a brain-storming exercise), I knowingly push broken code, and I change my mind about what this project even is for daily... when that's no longer true I'll replace this terrifying paragraph with some salesy piece about how much better food tastes with this module in your project (and I'll move to 1.x)

$ npm install steply

API is roughly 20% done and the code is fairly legible (says the dev who wrote it...;)

Promises are awesome, I love promises... but I'm not an academic and sometimes I'd find myself having naive thoughts like "I just want to call a() and then when that's done, b()"... or I'd find myself reading wikipedia pages on monads when all I really wanted was to call the next custom function with values calculated in the current custom function.

Basically when the Stepper executes a method it returns its self. every method called on Stepper is used to create a list of functions to be sequenced. there are 5 basic Stepper methods:

  • set the next function
  • set the next arguments
  • set the next target (the this the next function will use)
  • push the current-next function+arguments+target to the stack of steps
  • set and push an error handler to the stack
  • The additional methods are combination methods which are attempts to expressively solve common use cases

Once the Stepper is chain called to setup the steps the stack is executed

  • stacks are created for functions, arguments, and targets
  • if a Step has a function, arguments, or target defined it is pushed onto its respective stack
  • the top function, arguments, and target are combined and executed
  • if there is no result, the next Step is run
  • if there is a normal result, it's pushed onto the arguments stack, the next Step is run
  • if the result is a StepPauser then we're dealing with an asynchronous method and we setup a continue method on the returned StepPauser
  • when the async method is complete, it should call the continue method with any results. those results are appended to the arguments stack and the next Step is run

calling exec() will push any targets, functions, and arguments to their respective stacks (hopefully that will make sense later)

can also be passed a function or an array to be used for the current step

sets the function to be pushed onto the list of steps

Stepply().fun(foo).exec() //execute foo 
         .fun(bar).exec(); //once foo is done, execute bar 
function foo() {...}
function bar() {...}

for when functions alone won't do it

Stepply().args(1, 2, 3).fun(foo).exec() //execute foo(1, 2, 3) 
         (4, 5, 6).exec();         //once foo is done, call it again with (4, 5, 6) 
function foo(abc) {...}

very similar to args...

Stepply().args([1, 2, 3]).fun(foo).exec() //execute foo(1, 2, 3) 
         .args([4, 5, 6]).exec();         //once foo is done, call it again with (4, 5, 6) 
function foo(abc) {...}

set the target any functions will refer to as this

var thing1 = {bar:"thing1's bar"};
var thing2 = {bar:"thing2's bar"};
    .obj(thing1).exec()  //logs "thing1's bar" 
    .obj(thing2).exec(); //logs "thing2's bar" 
function foo() {

set function for handling any thrown errors

Stepply().fun(throwy).exec() //error thrown... 
    .fun(foo).exec()         //skipped 
    .fun(bar).exec()         //skipped 
    .err(catchy)             //catches and handles error 
    .fun(baz).exec();        //runs 
function throwy() {
    throw new Error(...);
function catchy(error) {

depending on the signature: sets target, sets arguments, sets function, and/or executes

Stepply().then(target1, method1, 1, 2, 3)
         .then(target2, method2, 4, 5)

for more information see ... (TODO: deep dive into then signatures)

logs the current arguments in the stack. if it's called with an argument, the argument is used as a label

Stepply().args(1, 2).log() //logs "1, 2" 
         .args(3).log('a');//logs "a: 3" 

passes current arguments to every function in the paramaters. next step is called after all functions complete

Stepply().all(foo, bar, baz) // calls foo(), bar(), and baz() simultaneously 
         .log("results");    // logs "results: [foo()'s results...], [bar()'s results...], [baz()'s results...]" 

calls next step after some number of milliseconds

Stepply().then(doSomething) //do something 
         .wait(2000)        //do nothing for 2 seconds 
         .then(doSomething) //do something again 

wrap node style function so that callbacks go to next step and errors are thrown

Stepply().args("some.filepath").node(fs.stat).log(); //logs stat object for some.filepath 

like node, but for node functions who's callbacks don't ever error

Stepply().args("some.filepath").nodeNoErr(fs.exists).log(); //logs if some.filepath exists 

TODO: figure out if this is something that doesn't require a pull request