Async waterfall in 131bytes (short) / 209bytes (long) with custom scopes

async-waterfall-131bytes.js

// 131bytes/short version
// jsbin demo http://jsbin.com/hakila/5/edit?console,js
function awf(n,t,l){!function c(){t.length>0?t.shift().apply(n||{},[].slice.call(arguments).concat(c)):0,0==t.length?l.call(n):0}()}

async-waterfall-209bytes.js

// 209bytes/long version
// jsbin demo http://jsbin.com/hakila/5/edit?console,js
function awf(scope, funcs, end) {
  (function next() {
    funcs.length > 0 ? funcs.shift().apply(scope || {}, [].slice.call(arguments).concat(next)) : 0;
    funcs.length == 0 ? end.call(scope) : 0;
  })();
}

example-usage.js

// jsbin demo http://jsbin.com/hakila/5/edit?console,js
var obj = {
  stage1: 0,
  stage2: 10,
  nested: {
    observer: 200,
    finish: 'end'
  }
};
 
 
//scope: obj
awf(obj, [
  function step1(next) {
    console.log('obj.stage1 at `step1`:'+this.stage1);
    next();
  },
  function step2(next) {
    console.log('obj.nested.observer at `step2`:'+this.nested.observer);
    console.log('increment it with 100');
    var newObserverValue = this.nested.observer+100
    next(newObserverValue);
  },
  function step3(newObserver, next) {
    console.log('obj.nested.observer at `step3` is '+newObserver+' - incremented at `step2`, now setTimeout at `step3`');
    setTimeout(function() {
      newObserver = newObserver+200
      console.log('obj.nested.observer at `step3`: '+newObserver);
      next(newObserver);
    }, 500);
  },
  function step4(newNewObserverValue, next) {
    //next is undefined, not call it
    console.log('obj.nested.observer now at `step4: '+newNewObserverValue)
  },
],
function done() {
  console.log('example 1 finished');
  console.log('------- wait 3s for next example to load ------');
});
  
  
//scope:obj.nested
//will set timeout 3000ms for demo reasons
setTimeout(function() {
awf(obj.nested, [
  function one(next) {
    console.log('obj.nested.observer inital: '+this.observer);
    var self = this, obsrv;
    setTimeout(function() {
      obsrv = self.observer+100;
      console.log('obj.nested.observer increments at `one` with 100 and proceed');
      next(obsrv);
    }, 200);
  },
  function two(obsrv, next) {
    var self = this;
    setTimeout(function() {
      console.log('obj.nested.observer at `two`: '+obsrv);
      next(obsrv);
    }, 500);
  },
  function tree(obsrvFinal, next) {
    // next == undefined, cuz no more funcs in waterfall
    console.log('obj.nested.observer at `tree`: '+(obsrvFinal+1));
  }], 
  function done() {
    console.log(this.finish + '`ed')
  }
);
},3000);

z-awf-as-promise.js

function catchy(funcs, end) {
  var reject = function reject(err) {
    funcs = [];
    end.call(this, err);
    return;
  };

  var resolve = function resolve() {
    if (funcs.length === 0) {
      end.call(this, null, [].slice.call(arguments))
      return;
    }
    if (funcs && Array.isArray(funcs)) {
      funcs.shift().apply(this, [].slice.call(arguments).concat([resolve, reject]))
    }
  };
  
  setTimeout(resolve, 0)
}

var data = 'str'

catchy([
  function then1(resolve, reject) {
    if (typeof data == 'string') {
      console.log('1 [pass] $data is `string`')
      resolve(data+123)
      return;
    }
    reject(new TypeError('1 [fail] $data must be `string`'))
  },
  function then2(data, resolve, reject) {
    if (data == 'str123') {
      console.log('2 [pass] $data is `str123`')
      setTimeout(function() {
        resolve([data, 123, true])
      }, 500)
      return;
    }
    reject(new Error('2 [fail] $data must be `str123`'))
  },
  function then3(data, resolve, reject) {
    if (Array.isArray(data) && data.length == 3) {
      console.log('3 [pass] $data is `array`')
      console.log('3 [pass] $data is with length 3')
      resolve(data);
      return;
    }
    reject(new Error('3 [fail] $data must be array with length 3'))
  },
  function then4(data, resolve, reject) {
    if (data[1] === 123) {
      setTimeout(function() {
        console.log('4 [pass] $data[1] is `123`, convert to `yes123`')
        data[1] = 'yes123'
        resolve(data, 'hello here')
      },200)
      return;
    }
    reject(new Error('4 [fail] $data[1] should be `123` {Number}'))
  },
  function then5(data, second, resolve, reject) {
    if (data[1] === 'yes123' && second === 'hello here') {
      console.log('5 [pass] $data[1] is `yes123`')
      console.log('5 [pass] $second is `hello here`')
      resolve(12, data, second)
      return;
    }
    reject(new Error('5 [fail] $data[1] should be `yes123` {String} and $second should be `hello here`'))
  }],
function done(err, res) {
  if (err) {
    console.error(err)
    return;
  }
  console.log('Completed successfully!', res)
})