savoy

Savoy.js

Higher-order functions (synchronous and asynchronous each/eachSeries/map/filter/fold) and functions for flow control (parallel/series/waterfall) in under 1 KB.

• API is similar (not identical) to that of the Async library
• 2.5 KB minified, or about 0.9 KB minified and gzipped
• Legible tests, with 100% coverage

Why

Savoy’s higher-order functions differ from Async’s in the following ways:

• The signature of the fn iterator is different. The cb callback (invoked to signal the end of each iteration of fn) is the first argument of fn. In addition, fn is also passed the index/key of the current element, and the original collection itself.
• If passed is an Object, map and filter will return an Object. (If passed an Object, Async’s map and filter will return an Array.)

Also, mainly this:

Inventing your own wheels gives you a deep appreciation and understanding of how wheels work and what makes a good one.

API

In all of the method signatures below, collection (in each/eachSeries/map/filter/fold) and fns (in parallel/series/waterfall) can either be an Array or an Object literal.

• each
• eachSeries
• map
• filter
• fold
• parallel
• series
• waterfall

each

savoy.each(collection, fn) — synchronous each

savoy.each([1, 2, 3], function(val, i, arr) {
  console.log(val, i, arr);
  //=> 1, 0, [ 1, 2, 3 ]
  //=> 2, 1, [ 1, 2, 3 ]
  //=> 3, 2, [ 1, 2, 3 ]
});

• Break from the loop by explicitly returning false from fn:

  savoy.each([1, 2, 3], function(val, i, arr) {
    console.log(val, i, arr);
    //=> 1, 0, [ 1, 2, 3 ]
    //=> 2, 1, [ 1, 2, 3 ]
    if (i === 1) {
      return false;
    }
  });

savoy.each(collection, fn, done) — asynchronous each

savoy.each({ a: 1, b: 2, c: 3 }, function(cb, val, key, obj) {
  console.log(val, key, obj);
  //=> 1, 'a', { a: 1, b: 2, c: 3 }
  //=> 2, 'b', { a: 1, b: 2, c: 3 }
  //=> 3, 'c', { a: 1, b: 2, c: 3 }
  cb();
}, function(err) {
  console.log(err);
  //=> null
});

• The asynchronous function fn is called in parallel over each item in collection.
• Invoke the cb callback in fn to signal the end of each iteration of fn.
• The signature of the cb callback is cb(err). If err is truthy, the done callback is called exactly once with the err.
• When fn has completed execution over every item in the collection, the done callback is called exactly once with a falsy err.

eachSeries

savoy.eachSeries(collection, fn) — synchronous eachSeries

• Alias of savoy.each.

savoy.eachSeries(collection, fn, done) — asynchronous eachSeries

savoy.each({ a: 1, b: 2, c: 3 }, function(cb, val, key, obj) {
  console.log(val, key, obj);
  //=> 1, 'a', { a: 1, b: 2, c: 3 }
  //=> 2, 'b', { a: 1, b: 2, c: 3 }
  //=> 3, 'c', { a: 1, b: 2, c: 3 }
  cb();
}, function(err) {
  console.log(err);
  //=> null
});

• The asynchronous function fn is called in series over each item in collection.
• Invoke the cb callback in fn to signal the end of each iteration of fn.
• The signature of the cb callback is cb(err). If err is truthy, we stop iterating over the collection, and the done callback is called exactly once with the err.
• When fn has completed execution over every item in the collection, the done callback is called exactly once with a falsy err.

map

savoy.map(collection, fn) — synchronous map

var result = savoy.map({ a: 1, b: 2, c: 3 }, function(val, key, obj) {
  console.log(val, key, obj);
  //=> 1, 'a', { a: 1, b: 2, c: 3 }
  //=> 2, 'b', { a: 1, b: 2, c: 3 }
  //=> 3, 'c', { a: 1, b: 2, c: 3 }
  return val * 2;
});
console.log(result);
//=> { a: 2, b: 4, c: 6 }

savoy.map(collection, fn, done) — asynchronous map

savoy.map([1, 2, 3], function(cb, val, i, arr) {
  console.log(val, i, arr);
  //=> 1, 0, [1, 2, 3]
  //=> 2, 1, [1, 2, 3]
  //=> 3, 2, [1, 2, 3]
  cb(null, val * 2);
}, function(err, result) {
  console.log(err, result);
  //=> null, [2, 4, 6]
});

• The asynchronous function fn is called in parallel over each item in collection.
• Invoke the cb callback in fn to signal the end of each iteration of fn. The signature of the cb callback is cb(err, mapVal):
  1. err — If truthy, the done callback is called exactly once with the err.
  2. mapVal — This is accumulated in the result argument of the done callback.
• When fn has completed execution over every item in the collection, the done callback is called exactly once with a falsy err and the result of the map.
• Note that if collection is an Object:
  1. result will also be an Object.
  2. Items in result may not be in the same order as their corresponding items in the original collection.

filter

savoy.filter(collection, fn) — synchronous filter

var result = savoy.filter([1, 2, 3], function(val, i, arr) {
  console.log(val, i, arr);
  //=> 1, 0, [1, 2, 3]
  //=> 2, 1, [1, 2, 3]
  //=> 3, 2, [1, 2, 3]
  return val > 1;
});
console.log(result);
//=> [2, 3]

savoy.filter(collection, fn, done) — asynchronous filter

savoy.filter({ a: 1, b: 2, c: 3 }, function(cb, val, key, obj) {
  console.log(val, key, obj);
  //=> 1, 'a', { a: 1, b: 2, c: 3 }
  //=> 2, 'b', { a: 1, b: 2, c: 3 }
  //=> 3, 'c', { a: 1, b: 2, c: 3 }
  cb(null, val > 1);
}, function(err, result) {
  console.log(err, result);
  //=> null, { b: 2, c: 3 }
});

• The asynchronous function fn is called in parallel over each item in collection.
• Invoke the cb callback in fn to signal the end of each iteration of fn. The signature of the cb callback is cb(err, predicate):
  1. err — If truthy, the done callback is called exactly once with the err.
  2. predicate — If truthy, the current item is added to the result argument of the done callback.
• When fn has completed execution over every item in the collection, the done callback is called exactly once with a falsy err and the result of the filter.
• Note that if collection is an Object:
  1. result will also be an Object.
  2. Items in result may not be in the same relative order as they were in collection.

fold

savoy.fold(collection, acc, fn) — synchronous fold

var result = savoy.fold({ a: 1, b: 2, c: 3 }, 0, function(acc, val, key, obj) {
  console.log(acc, val, key, obj);
  //=> 1, 'a', { a: 1, b: 2, c: 3 }
  //=> 2, 'b', { a: 1, b: 2, c: 3 }
  //=> 3, 'c', { a: 1, b: 2, c: 3 }
  return acc + val;
});
console.log(result);
//=> 6

savoy.fold(collection, acc, fn, done) — asynchronous fold

savoy.fold([1, 2, 3], 0, function(cb, acc, val, i, arr) {
  console.log(acc, val, i, arr);
  //=> 0, 1, 0, [1, 2, 3]
  //=> 1, 2, 1, [1, 2, 3]
  //=> 3, 3, 2, [1, 2, 3]
  cb(null, acc + val);
}, function(err, result) {
  console.log(err, result);
  //=> null, 6
});

• The asynchronous function fn is called in series over each item in collection.
• Invoke the cb callback in fn to signal the end of each iteration of fn. The signature of the cb callback is cb(err, foldVal):
  1. err — If truthy, the done callback is called exactly once with the err.
  2. foldVal — This is the value for acc that is passed to the next iteration of fn.
• When fn has completed execution over every item in the collection, the done callback is called exactly once with a falsy err and the result of the fold.

parallel

savoy.parallel(fns [, done])

savoy.parallel([
  function(cb) {
    cb(null, 1);
  },
  function(cb) {
    cb(null, 2);
  },
  function(cb) {
    cb(null, 3);
  }
], function(err, result) {
  console.log(err, result);
  //=> null, [1, 2, 3]
});

• Each function in fns is called in parallel.
• Invoke the cb callback in each function to signal the end of the function. The signature of the cb callback is cb(err, val):
  1. err — If truthy, the done callback is called exactly once with the err.
  2. val — This is accumulated in the result argument of the done callback.
• When every function in fns has completed execution, the done callback is called exactly once with a falsy err and the result of each function.

series

savoy.series(fns [, done])

savoy.series({
  a: function(cb) {
    cb(null, 1);
  },
  b: function(cb) {
    cb(null, 2);
  },
  c: function(cb) {
    cb(null, 3);
  }
}, function(err, result) {
  console.log(err, result);
  //=> null, { a: 1, b: 2, c: 3 }
});

• Each function in fns is called in series.
• Invoke the cb callback in each function to signal the end of the function. The signature of the cb callback is cb(err, val):
  1. err — If truthy, the done callback is called exactly once with the err.
  2. val — This is accumulated in the result argument of the done callback.
• When the entire series of functions has completed execution, the done callback is called exactly once with a falsy err and the result of each function.

waterfall

savoy.waterfall(fns [, done])

savoy.waterfall([
  function(cb) {
    cb(null, 'a', 'b');
  },
  function(cb, arg1, arg2) {
    console.log(arg1, arg2);
    //=> 'a', 'b'
    cb(null, 'c');
  },
  function(cb, arg) {
    console.log(arg);
    //=> 'c'
    cb(null, 'd', 'e');
  }
], function(err, arg1, arg2) {
  console.log(err, arg1, arg2);
  //=> null, 'd', 'e'
});

• Each function in fns is called in series.
• Invoke the cb callback in each function to signal the end of the function. The signature of the cb callback is cb(err [, arg1, arg2, ...]):
  1. err — If truthy, the done callback is called exactly once with the err.
  2. arg1, arg2, ... — Arguments that are passed on to the next function in fns.
• When the entire series of functions has completed execution, the done callback is called exactly once with a falsy err and arguments from the last function in fns.

Installation

Install via npm:

$ npm i --save savoy

Install via bower:

$ bower i --save yuanqing/savoy

To use Savoy in the browser, include the minified script in your HTML:

<body>
  <!-- ... -->
  <script src="path/to/savoy.min.js"></script> 
  <script>
    // savoy available here
  </script> 
</body>

License

MIT