enQue.js

Chain asynchronous functions in succession, consuming the same data stream.

const Que = new require('enQue');
Que([fn1, fn2, fn3, fn4, fn5]).run(data).then(CALLBACK); // .then(function(arguments){});
// Where each fn follows the format fn(data, next) { /*example: */ data.size++; next() } 
// data must be an OBJECT! ie: myQue.run({text:"Hi"}) then in your callback its data.text

For full documentation see the enQue full docs.

Features

1.) Skip ahead in the que next(4) would skip to position 4.

2.) Go backwards in the que next(-4) would go back 4.

3.) Inject a Function at a particular que index next({inject:4,function:Function}). (runs parallel to que not sync'd)

4.) Quit after a specified amount of que spots next({quit:4}) quits after 4 more iterations.

5.) Allows removing functions from the que by index, variable name, or raw strings (experimental regex's).

6.) A fill method for convenience.

The above code snippet illustrates how simple it would be to execute 5 asynchronous functions in succession that all operate on the same data. When you add a function to the que accept the second a parameter (data is first) and make sure to call it for example FUNCTION_NAME(data, next) { /* example: */ data.size + 1; /* MANDATORY */ next() }. You can also use next(0) to quit early. The entire point of this package is that each spot in the que wont run untill the last spot has said ok im done via calling next(), or whatever you chose to name it.

Since a promise is returned it is always best to attach a .then() and .catch() so the above code would become.

myQue.run(data)
  .then(sucessCallback); // Passed 1 argument, the data OBJECT.
  .catch(errorCallback); // Passed 1 argument, the error.

Instalation

npm install enque

Dependencies

None.

Usage examples

// USAGE EXAMPLE
const Que = require('enQue');
const que = new Que();

// Used to only go backwards once, otherwise you end up in an infinite cycle.
// IF YOU GO FORWARD IN THE QUE YOU CANNOT GO BACKWARDS TO A PLACE NOT ON THE NEW QUE
// It will throw a error if you attempt to go forward then backwards.
var once = true;

que.add((data, next, done, index) => {
  // index is the position of your function in the que, 0 right now.
  //return done(); // You can return early if you'd like
  setTimeout(()=>{
    data.msg += ' ONE';
    // You can inject a function at a specified relative position (it isnt added to the que, it runs parallel so careful here).
    //next({inject:7, function: function(data) {data.msg += " ONE AND A HALF";}}); // This would run that function after 7 more que'd fn's are done.
    next()
  }, 9000)
});
que.add((data, next) => {
  setTimeout(()=>{
    //throw "errors work too" // You can throw an error and reject the promise
    data.msg += ' TWO';
    next();
  }, 4000)
});
que.add((data, next) => {
  data.msg += ' THREE';
  next()
});

function myFn1(data, next) {
  data.msg += ' FOUR';
  // You can go backwards in the que.
  if(once) { once = false; next(-2); }
  // You can go forwards in the que.
  else next(1);
}

function myFn2(data, next) {
  data.msg += ' FIVE';
  next();
}

// You can add multiple functions at a time.
que.add([myFn1, myFn2]) 

que.run({msg: 'ZERO'})
  .then(res => console.log(res.msg))
  .catch(err => console.log('Woopsie! ' + err))

Executing the above code as is gives:

ONE TWO THREE FOUR TWO THREE FOUR FIVE

More examples

NOTE You can't actually call que.run() then que.clear() because the que may still be processing. You need to call. que.run().then(()=>que.clear()) or to extract data from the processed que que.run().then(data=>YOUR_CALLBACK(data)). Each function in your que is handed data as a first parameter whether or not you originally passed one in. default {}

// For the purpose of these examples, assume each function is asynchronous and you don't know when it will finish execution.
// When operating on the data it is important to remember that it must not be a primitive. If you must operate on just a primitive
// set it to an attribute on an object. for example if you need to operate on a `Number` you can do `que.run({data.number=17})`.

Que = require('enQue');
que = new Que();

function fn1(data, next) {
 console.log(1);
 next();
}
function fn2(data, next) {
 console.log(2);
 next();
}

que.add(fn1);
que.run(); // 1
que.clear();

que.add([fn1, fn1, fn1]);
que.run(); // 1 1 1
que.clear();

que.fill(fn1, 7);
que.run();
que.clear(); // 1 1 1 1 1 1 1 

que.add([fn1, fn1, fn1]);
que.remove(fn1);
que.run(); // ""

que.add([fn1, fn2, fn2, fn2]);
que.remove([fn1, fn2], 3); // for best preformance only pass in numbers i.e. `remove(0); remove(1); remove(2)`
que.run(); // 2
que.clear();

que.add([(d,n)=>n(5), fn1, fn1, fn1, fn1, fn1, fn1]);
que.run(); // 1
que.clear();

que.add([(d,n)=>n({quit:3}), fn1, fn1, fn1, fn2, fn2, fn2]);
que.run(); // 1 1 1
que.clear();

que.add((d,n,i)=>{console.log("hi"); n()});
que.remove('(d,n,i)=>{console.log("hi"); n()}');
que.run(); // ""

fn5 = (data, next, index, done) => {
  console.log(index);
  index === 2 ? next(0) : next();
  // instead of next(0) you can use done()
}

que.add([fn5, fn5, fn5, fn5, fn5]);
que.run(); // 0 1 2
que.clear();

fn3 = (data, next) => {
 data.data = "SEVEN";
 next();
}

que.add([(d,n)=>n({inject:5, function: function(d){d.data="7"}}), fn3, fn3, fn3, fn3, fn3]);
que.run().then(res=>console.log(res)); // d.data === 7
// To initialise the data use `run(data)` where data is an Object.
que.clear();

function fn6(data, next, index) {
  throw new Error("Woopsie!");
  next();
}

que.add([fn6, fn6, fn6, fn6, fn6]);
que.run().catch(e=>console.log(e)); // prints the thrown error.

Executing the above code as is gives:

1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
0
1
2
{ data: '7' }
Error: Woopsie!
    at fn6 (...)
    at options (...)
    at enQue.executeQue (...)
    at ...
    ...

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