[JavaScript] 非同期処理のコールバック地獄から抜け出す方法 ref: http://qiita.com/LightSpeedC/items/7980a6e790d6cb2d6dad

aa-chan1.js

'use strict';

var aa = require('aa');
var Channel = aa.Channel;
var get = require('./get');

aa(function*() {
  var ch = Channel();

  get('a.txt', ch);
  var a = yield ch;

  get('b.txt', ch);
  var b = yield ch;

  get('c.txt', ch);
  var c = yield ch;

  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

aa-chan2.js

'use strict';

var aa = require('aa');
var Channel = aa.Channel;
var get = require('./get');

aa(function*() {
  var ch_a = Channel();
  var ch_b = Channel();
  var ch_c = Channel();

  get('a.txt', ch_a);
  get('b.txt', ch_b);
  get('c.txt', ch_c);
  var a = yield ch_a;
  var b = yield ch_b;
  var c = yield ch_c;

  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

aa-chan3.js

'use strict';

var aa = require('aa');
var Channel = aa.Channel;
var get = require('./get');

aa(function*() {
  var ch_a = Channel();
  var ch_b = Channel();
  var ch_c = Channel();

  get('a.txt', ch_a);
  get('b.txt', ch_b);
  var a = yield ch_a;
  var b = yield ch_b;

  get('c.txt', ch_c);
  var c = yield ch_c;

  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

aa-chan4.js

'use strict';

var aa = require('aa');
var Channel = aa.Channel;

var ch1 = Channel();
var ch2 = Channel();

// *** FIRST THREAD ***
aa(function*() {
  // send
  ch2('(a)');

  // receive
  var b = yield ch1;
  console.log(b);

  // send
  ch2('(c)');

  console.log('end of thread 1');
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

// *** SECOND THREAD ***
aa(function*() {
  // receive
  var a = yield ch2;

  // send
  ch1('(b)');

  // receive
  var c = yield ch2;

  console.log(a + c);
  console.log('end of thread 2');
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

aa-get1.js

'use strict';

var aa = require('aa');
var get = aa.thunkify(require('./get'));

aa(function*() {
  var a = yield get('a.txt');
  var b = yield get('b.txt');
  var c = yield get('c.txt');
  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

aa-get2.js

'use strict';

var aa = require('aa');
var get = aa.thunkify(require('./get'));

aa(function*() {
  var res = yield {a: get('a.txt'),
                   b: get('b.txt'),
                   c: get('c.txt')};
  console.log(res.a + res.b + res.c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

aa-get3.js

'use strict';

var aa = require('aa');
var get = aa.thunkify(require('./get'));

aa(function*() {
  var res = yield {a: get('a.txt'),
                   b: get('b.txt')};
  res.c = yield get('c.txt');
  console.log(res.a + res.b + res.c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

callback-hell1.js

'use strict';

var get = require('./get');

get('a.txt', function (err, a) {
  get('b.txt', function (err, b) {
    get('c.txt', function (err, c) {
      console.log(a + b + c);
    });
  });
});

callback-hell2.js

'use strict';

var get = require('./get');

var n = 0;
var res = {};

++n;
get('a.txt', function (err, a) {
  res.a = a;
  if (--n === 0) callback(null, res);
});

++n;
get('b.txt', function (err, b) {
  res.b = b;
  if (--n === 0) callback(null, res);
});

++n;
get('c.txt', function (err, c) {
  res.c = c;
  if (--n === 0) callback(null, res);
});

function callback(err, res) {
  console.log(res.a + res.b + res.c);
}

callback-hell3.js

'use strict';

var get = require('./get');

var n = 0;
var res = {};

++n;
get('a.txt', function (err, a) {
  res.a = a;
  if (--n === 0) callback(null, res);
});

++n;
get('b.txt', function (err, b) {
  res.b = b;
  if (--n === 0) callback(null, res);
});

function callback(err, res) {
  get('c.txt', function (err, c) {
    res.c = c;
    console.log(res.a + res.b + res.c);
  });
}

co-chan1.js

'use strict';

var co = require('co');
var chan = require('co-chan');
var get = require('./get');

co(function*() {
  var ch = chan();

  get('a.txt', ch);
  var a = yield ch;

  get('b.txt', ch);
  var b = yield ch;

  get('c.txt', ch);
  var c = yield ch;

  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

co-chan2.js

'use strict';

var co = require('co');
var chan = require('co-chan');
var get = require('./get');

co(function*() {
  var ch_a = chan();
  var ch_b = chan();
  var ch_c = chan();

  get('a.txt', ch_a);
  get('b.txt', ch_b);
  get('c.txt', ch_c);
  var a = yield ch_a;
  var b = yield ch_b;
  var c = yield ch_c;

  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

co-chan3.js

'use strict';

var co = require('co');
var chan = require('co-chan');
var get = require('./get');

co(function*() {
  var ch_a = chan();
  var ch_b = chan();
  var ch_c = chan();

  get('a.txt', ch_a);
  get('b.txt', ch_b);
  var a = yield ch_a;
  var b = yield ch_b;

  get('c.txt', ch_c);
  var c = yield ch_c;

  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

co-chan4.js

'use strict';

var co = require('co');
var chan = require('co-chan');

var ch = chan();

// *** FIRST THREAD ***
co(function*() {
  // send sync
  yield ch('(a)');

  // receive
  var b = yield ch;
  console.log(b);

  // send async
  ch('(c)');

  console.log('end of thread 1');
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

// *** SECOND THREAD ***
co(function*() {
  // receive
  var a = yield ch;

  // send sync
  yield ch('(b)');

  // receive
  var c = yield ch;

  console.log(a + c);
  console.log('end of thread 2');
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

co-get-thunk.js

'use strict';

var get = require('./get');

function co_get(file) {
  return function (callback) {
    get(file, callback);
  };
}

// var thunkify = require('thunkify');
// var co_get = thunkify(get);

module.exports = co_get;

co-get.js

'use strict';

var get = require('./get');

function co_get(file) {
  return new Promise(function (resolve, reject) {
    get(file, function (err, value) {
      if (err) reject(err);
      else resolve(value);
    });
  });
}

module.exports = co_get;

co-get1.js

'use strict';

var co = require('co');
var get = require('./co-get');

co(function*() {
  var a = yield get('a.txt');
  var b = yield get('b.txt');
  var c = yield get('c.txt');
  console.log(a + b + c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

co-get2.js

'use strict';

var co = require('co');
var get = require('./co-get');

co(function*() {
  var res = yield {a: get('a.txt'),
                   b: get('b.txt'),
                   c: get('c.txt')};
  console.log(res.a + res.b + res.c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

co-get3.js

'use strict';

var co = require('co');
var get = require('./co-get');

co(function*() {
  var res = yield {a: get('a.txt'),
                   b: get('b.txt')};
  res.c = yield get('c.txt');
  console.log(res.a + res.b + res.c);
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

file10.txt

$ node aa-get1.js

file11.txt

$ node --harmony co-get1.js

file12.txt

$ node aa-get2.js

file13.txt

$ iojs co-get1.js

file14.txt

$ node aa-get3.js

file15.txt

$ node --harmony co-get3.js

file16.txt

$ node aa-chan1.js

file17.txt

$ node --harmony co-get2.js

file18.txt

$ node aa-chan2.js

file19.txt

$ iojs co-get3.js

file2.txt

$ node callback-hell1.js

file20.txt

$ node aa-chan3.js

file21.txt

$ node --harmony co-chan3.js

file22.txt

$ node aa-chan4.js

file23.js

var ch = Channel();
ch.stream(socket);
// socket.on('end', ch.end);
// socket.on('error', ch);
// socket.on('readable', ch.readable);

var buff;
while (buff = yield ch) {
  console.log(String(buff));
}

file23.txt

$ npm i co-chan -S
$ node --harmony co-chan1.js

file24.js

'use strict';

var aa = require('aa');

aa(function*() {
  var ary = [1, 2, 3];

  ary.forEach(function (val) {
    console.log(val);
  });
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

file25.js

'use strict';

var aa = require('aa');

aa(function*() {
  var ary = [1, 2, 3];

  return yield ary.map(val => function* () {
    console.log(val);
    yield Promise.resolve(val);
  });
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

file25.txt

$ iojs co-chan2.js

file26.txt

$ node --harmony co-chan2.js

file28.txt

$ iojs co-chan3.js

file29.txt

$ node --harmony co-chan3.js

file31.txt

$ iojs co-chan4.js

file32.txt

$ node --harmony co-chan4.js

file33.js

var ch = chan();
ch.stream(socket);
// socket.on('end', ch.end);
// socket.on('error', ch);
// socket.on('readable', ch.readable);

while (!ch.done()) {
  var buff = yield ch;
  if (!buff) break;
  console.log(String(buff));
}

file34.js

'use strict';

var co = require('co');

co(function*() {
  var ary = [1, 2, 3];

  ary.forEach(function (val) {
    console.log(val);
  });
}).then(
  function (val) { console.info('ok: ' + val); },
  function (err) { console.error('ng: ' + err); });

file4.txt

$ node callback-hell2.js

file6.txt

$ node callback-hell3.js

get.js

'use strict';

function get(file, callback) {
  console.log('file: %s...', file);
  setTimeout(function () {
    console.log('file: %s complete', file);
    callback(null, '(' + file + ')');
  }, 200 + Math.random() * 100);
}

module.exports = get;

npm-install-aa-save.sh

$ npm install aa --save

npm-install-aa.sh

$ npm i aa -S

npm-install-co-save.sh

$ npm install co --save

npm-install-co.sh

$ npm i co -S

npm-install-thunkify.sh

$ npm install thunkify