nue

nue — An async control-flow library

nue is an async control-flow library suited for the node event loop.

Installing

$ npm install nue

Example

var nue = require('nue');
var flow = nue.flow;
var fs = require('fs');

var myFlow = flow(
  function (file) {
    fs.readFile(file, 'utf-8', this.async());
  },
  function (data) {
    if (this.err) throw this.err;
    console.log(data);
  }
);

myFlow('file1');

API Overview

Core

• flow

Serial

• map
• forEach
• filter
• every
• some
• queue

Parallel

• parallel
• parallelMap
• parallelForEach
• parallelFilter
• parallelEvery
• parallelSome
• parallelQueue

API Detail

### flow([Function tasks...]) -> Function

Return a function which represents the control-flow.

Arguments

• tasks: Optional. Tasks which are executed in series.

Context

this context of the each task has following properties.

• next: Function. A function to execute a next task.
• async: Function. A function to accept parameters for a next task and return a callback, which executes a next task.
• end: Function. A function to execute a last task to end a control-flow. The first parameter is an error object.

In addition to the above ones, the context of the last task has a following property.

• err: Object. An object represents an error which passed from the end function.

Example

var nue = require('nue');
var flow = nue.flow;
var fs = require('fs');

var myFlow = flow(
  function () {
    var results = [];
    fs.readFile('file1', this.async(results));
  },
  function (results, data) {
    results.push(data.length);
    fs.readFile('file2', this.async(results));
  },
  function (results, data) {
    results.push(data.length);
    this.next(results);
  },
  function (results) {
    if (this.err) throw this.err;
    console.log(results);
    this.next();
  }
);

myFlow();

### map(Function worker(arg)) -> Function

Return a function to process each value in series.

Arguments

• worker: Required. Function. A function to process each value.
• arg: Optional. Object. Each value passed from a previous task.

Context

this context of the worker has following properties.

• next: Function. A function to process next value.
• async: Function. A function to accept parameters for a next task and return a callback, which process next value.
• end: Function. A function to execute a last task to end a control-flow. The first parameter is an error object.
• isFirst: Boolean. Indicate whether the worker is handling the first value or not.
• isLast: Boolean. Indicate whether the worker is handling the last value or not.
• index: Number. An index of value.

Example

var nue = require('nue');
var flow = nue.flow;
var map = nue.map;
var fs = require('fs');

var myFlow = flow(
  function () {
    this.next('file1', 'file2', 'file3');
  },
  map(function (name) {
    var self = this;
    fs.readFile(name, function (err, data) {
      if (err) throw this.end(err);
      self.next(data.length);
    });
  }),
  function (results) {
    if (err) throw err;
    console.log(results);
    this.next();
  }
);

myFlow();

### parallel([Function tasks...]) -> Function

Return a function to execute tasks in parallel.

Arguments

• tasks: Optional. Tasks which are executed in parallel.

Context

this context of each task has following properties.

• next: Function. A function to complete a task and wait other tasks to complete.
• async: Function. A function to accept parameters for a next task and return a callback, which complete a task and wait other tasks to complete.
• end: Function. A function to execute a last task to end a control-flow. The first parameter is an error object.

Example

var nue = require('nue');
var flow = nue.flow;
var parallel = nue.parallel;
var fs = require('fs');

var myFlow = flow(
  function () {
    this.next('file1', 'file2');
  },
  parallel(
    function (name) {
      var self = this;
      fs.readFile(name, function (err, data) {
        if (err) this.end(err);
        self.next(data.length);
      });
    },
    function (path) {
      var self = this;
      fs.stat(path, function (err, stats) {
        if (err) this.end(err);
        self.next(stats.isFile());
      });
    }
  ),
  function (results) {
    if (this.err) throw this.err;
    console.log(results);
    this.next();
  }
);

myFlow();

### parallelMap(Function worker(arg)) -> Function

Return a function to process each value in parallel.

Arguments

• worker: Optional. Function. A function to process each value.
• arg: Optional. Object. Each value passed from a previous task.

Context

this context of the worker has following properties.

• next: Function. A function to complete a processing and wait other processing to complete.
• async: Function. A function to accept parameters for a next task and return a callback, which complete a processing and wait other processing to complete.
• end: Function. A function to execute a last task to end a control-flow. The first parameter is an error object.

Example

var nue = require('nue');
var flow = nue.flow;
var parallelMap = nue.parallelMap;
var fs = require('fs');

var myFlow = flow(
  function () {
    this.next('file1', 'file2');
  },
  parallelMap(function (name) {
    var self = this;
    fs.readFile(name, function (err, data) {
      if (err) this.end(err);
      self.next(data.length);
    });
  }),
  function (results) {
    if (this.err) throw this.err;
    console.log(results);
    this.next();
  }
);

myFlow();