A simple flow wrapper for asynchronous function that can avoid callback hell on the basis of execution order.

Table of Contents

• Installation
• asynFlow
• Processor
• Flow

Installation

npm install node-processor

let asynFlow = require('node-processor').asynFlow;
let Processor = require('node-processor').Processor;
let Flow = require('node-processor').Flow;

asynFlow

required params

funcs: single asynchronous function or asynchronous function array.

function asyn1(options, callback) {
    console.log('asyn1', options);
    setTimeout(callback, 1000, null, 'result1');
}
function asyn2(options, callback) {
    console.log('asyn2', options);
    setTimeout(callback, 1000, 'this is an error', 'result2');
}
function asyn3(options, callback) {
    console.log('asyn3', options);
    setTimeout(callback, 1000, null, 'result3');
}

let funcs1 = asyn1;
let funcs2 = [asyn1];
let funcs3 = [asyn1, asyn2, asyn3];

xargs: single object param or object param array.

let xarg1 = { name: 'xarg1' };
let xarg2 = { name: 'xarg2' };
let xarg3 = { name: 'xarg3' };

let xargs1 = xarg1;
let xargs2 = [xarg1];
let xargs3 = [xarg1, xarg2, xarg3];

optional params

• ignoreError(default false):
  When error occurs in some stage of the process flow, left functions will be skipped and the callback will be called if it exists.
• returnXargs(default false):
  When it is true, xargs itself will be passed to the callback as the result.

four features

support various process situation

1. one asynchronous function with one xarg

asynFlow({funcs: funcs1, xargs: xargs1});

2. one asynchronous function with multi xarg

asynFlow({funcs: funcs1, xargs: xargs3});

3. multi asynchronous function with one xarg

asynFlow({funcs: funcs3, xargs: xargs1});

4. multi asynchronous function with multi xarg

asynFlow({funcs: funcs3, xargs: xargs3});

But, if the number of funcs is not equal with the number of xargs and they are neither 1, the asynFlow will not execute any function.

support recording error and result of every function

asynFlow({funcs: funcs3, xargs: xargs3}, function(error,result){
  console.log(result);
  //result is an array contains three objects like this {error:null, result:'result'}.
});

support skipping left functions when error occurs

asynFlow({funcs: funcs3, xargs: xargs3}, function(error,result){
  console.log(error);
  //error is an instance of Error with one description like 'Error occured in step 2'
  console.log(result);
  //result is an array contains two objects.
});

If ignoreError is set to be true, asynFlow will ignore every error and execute to the last step.

support return xargs in itself

When the returnXargs is true, the number of xargs must be 1.

asynFlow({funcs: funcs3, xargs: xargs1, returnXargs:true}, function(error,result){
  console.log(result);
  //result is just xargs1.
});

asynFlow({funcs: funcs3, xargs: xargs2, returnXargs:true}, function(error,result){
  console.log(result);
  //result is xargs2[0].
});

Processor

In order to be compatible with synchronous function and to make a certain abstract of process flow, processor class emerges as the times require. One processor is an object which contains a name and a function with a flag to mark whether it is asynchronous.

let processor1 = new Processor({
  asyn: true,
  name: 'step1',
  func: function(options,callback){
    console.log('step1', options);
    setTimeout(callback, 1000, null, 'result1');
  }
});

If the function is a synchronous function, it will be wrapped to accept one callback.

let processor2 = new Processor({
  asyn: false,
  name: 'step2',
  func: function(options){
    console.log('step2', options);
    return 'something';
  }
});

Flow

In essence flow is a collection of processor. Flow can add or remove processor dynamically by array index.

let flow = new Flow();//support ignoreError and returnXargs. 
flow.add(processor1);
flow.add(0,processor2);
flow.remove(1);

Flow can create a new flow which only contains some of primary processors by filter function.

let newFlow = flow.filter(function(processor){
  return processos.asyn;
});

Obviously, flow can execute just like asynFlow.

flow.execute(xargs1,function(error,result){
  console.log(error);//depends on whether there is a error and ignoreError.
  console.log(result);////depends on returnXargs.
});