Support series

README.md

@@ -23,6 +23,7 @@ All methods return a promise.
 
 - [filter](#filter)
 - [map](#map)
+- [series](#series)
 - [forEach](#foreach)
 - [reduce](#reduce)
 - [AsyncArray](#asyncarray)
@@ -60,7 +61,7 @@ filter(
 
 Signature: `map(arr, fn, context)`
 
-`fn` is called with elements in parallel.
+`fn` is called with each element in parallel.
 
 ```javascript
 map(
@@ -79,6 +80,38 @@ map(
 
 ```
 
+### series
+This method works like `map`,
+except that `fn` is called with each element in sequence rather than in parallel.
+
+Signature: `map(arr, fn, context)`
+
+
+```javascript
+var n = 1
+series(
+  [1, 2, 3, 4],
+  function (v, i, arr, next) {
+    var delay = rand()
+    console.log('i:', i, 'delay:', delay)
+    setTimeout(function() {
+      next(null, v << n++)
+    }, delay)
+  }
+)
+// i: 0 delay: 10
+// i: 1 delay: 50
+// i: 2 delay: 0
+// i: 3 delay: 80
+// [2, 8, 24, 64]
+.then(log)
+
+function rand() {
+  return Math.floor(Math.random() * 10) * 10
+}
+
+```
+
 ### forEach
 
 `fn` is called with elements in sequence.
@@ -125,6 +158,13 @@ reduce(
 ### AsyncArray
 Signature: `AsyncArray(arr)`
 
+Methods:
+* `map`
+* `series`
+* `filter`
+* `forEach`
+* `reduce`
+
 ```javascript
 var origin = AsyncArray([1, 2, 3, 4, 5, 6])
 var odd = origin.filter(isOdd)

example/series.js

@@ -0,0 +1,21 @@
+var series = require('..').series
+
+var log = console.log.bind(console)
+
+var n = 1
+series(
+  [1, 2, 3, 4],
+  function (v, i, arr, next) {
+    var delay = rand()
+    console.log('i:', i, 'delay:', delay)
+    setTimeout(function() {
+      next(null, v << n++)
+    }, delay)
+  }
+)
+// [2, 8, 24, 64]
+.then(log)
+
+function rand() {
+  return Math.floor(Math.random() * 10) * 10
+}

index.js

@@ -3,5 +3,6 @@ exports.forEach = require('./lib/forEach')
 exports.map = require('./lib/map')
 exports.filter = require('./lib/filter')
 exports.reduce = require('./lib/reduce')
+exports.series = require('./lib/series')
 exports.Array = require('./lib/async-array')
 

lib/async-array.js

@@ -1,5 +1,6 @@
 var asyncMethods = {
   map: require('./map'),
+  series: require('./series'),
   filter: require('./filter'),
   reduce: require('./reduce'),
   forEach: require('./forEach'),
@@ -12,7 +13,7 @@ function AsyncArray(arr) {
   this.result = Promise.resolve(arr || [])
 }
 
-['map', 'filter', 'forEach', 'reduce']
+['map', 'filter', 'forEach', 'reduce', 'series']
 .forEach(function (fnName) {
   AsyncArray.prototype[fnName] = function () {
     var args = slice(arguments)

lib/series.js

@@ -0,0 +1,18 @@
+var Runner = require('callback-sequence').Runner
+var runner = Runner({
+  run: { stream: false },
+})
+
+module.exports = function (arr, fn, ctx) {
+  if (arguments.length < 3) {
+    ctx = arr
+  }
+
+  return runner.series.apply(runner, arr.map(function (v, i) {
+    return fn.bind(ctx, v, i, arr)
+  })).then(function (results) {
+    return [].concat.apply([], results)
+  })
+}
+
+

package.json

@@ -28,7 +28,7 @@
   },
   "homepage": "https://github.com/zoubin/async-array-methods#readme",
   "dependencies": {
-    "callback-sequence": "^3.1.0"
+    "callback-sequence": "^3.2.0"
   },
   "devDependencies": {
     "eslint": "^1.5.1",

test/array.js

@@ -22,6 +22,20 @@ test('map', function(t) {
   })
 })
 
+test('series', function(t) {
+  var origin = AsyncArray([1, 3, 5])
+  var delays = [10, 0, 20]
+  return origin.series(function (v, i, arr, next) {
+    setTimeout(function() {
+      next(null, v + 1)
+    }, delays[i])
+  })
+  .then(function (res) {
+    t.same(res, [2, 4, 6])
+  })
+
+})
+
 test('reduce', function(t) {
   var origin = AsyncArray([1, 3, 5])
   return origin.reduce(function (a, b) {

test/series.js

@@ -0,0 +1,34 @@
+var test = require('tap').test
+var series = require('../lib/series')
+
+test('results', function(t) {
+  t.plan(2)
+
+  var res = []
+  series([30, 20, 10], function (v, i, arr, next) {
+    setTimeout(function() {
+      res.push(v)
+      next(null, i)
+    }, v)
+  }).then(function (results) {
+    t.same(results, [0, 1, 2])
+    t.same(res, [30, 20, 10])
+  })
+})
+
+test('context', function(t) {
+  t.plan(2)
+
+  var res = []
+  series([30, 20, 10], function (v, i, arr, next) {
+    var self = this
+    setTimeout(function() {
+      res.push(v)
+      next(null, i + self.n)
+    }, v)
+  }, { n: 1 }).then(function (results) {
+    t.same(results, [1, 2, 3])
+    t.same(res, [30, 20, 10])
+  })
+})
+