Merge pull request #246 from goatslacker/functional-tools

Functional tools

Author: goatslacker

src/utils/fp.js

@@ -0,0 +1,48 @@
+const { push } = Array.prototype
+
+// Disabling no-shadow so we can sanely curry
+/*eslint-disable no-shadow*/
+export function map(fn, stores) {
+  return stores
+    ? stores.map(store => fn(store.getState()))
+    : stores => map(fn, stores)
+}
+
+export function filter(fn, stores) {
+  return stores
+    ? stores.filter(store => fn(store.getState()))
+    : stores => filter(fn, stores)
+}
+
+export function reduce(fn, stores, acc = {}) {
+  return stores
+    ? stores.reduce((acc, store) => fn(acc, store.getState()), acc)
+    : stores => reduce(fn, stores)
+}
+
+export function flatMap(fn, stores) {
+  if (!stores) return (stores) => flatMap(fn, stores)
+
+  return stores.reduce((result, store) => {
+    let value = fn(store.getState())
+    if (Array.isArray(value)) {
+      push.apply(result, value)
+    } else {
+      result.push(value)
+    }
+    return result
+  }, [])
+}
+
+export function zipWith(fn, a, b) {
+  if (!a && !b) {
+    return (a, b) => zipWith(fn, a, b)
+  }
+
+  const length = Math.min(a.length, b.length)
+  const result = Array(length)
+  for (let i = 0; i < length; i += 1) {
+    result[i] = fn(a[i].getState(), b[i].getState())
+  }
+  return result
+}

test/functional-tools-test.js

@@ -0,0 +1,102 @@
+import { assert } from 'chai'
+import Alt from '../'
+import { createStore } from '../utils/decorators'
+import { map, filter, reduce, flatMap, zipWith } from '../utils/fp'
+
+const alt = new Alt()
+
+@createStore(alt)
+class Store1 {
+  constructor() {
+    this.a = 1
+    this.num = 1
+    this.arr = [1, 2, 3]
+  }
+}
+
+@createStore(alt)
+class Store2 {
+  constructor() {
+    this.b = 2
+    this.num = 2
+    this.arr = [4, 5, 6]
+  }
+}
+
+@createStore(alt)
+class Store3 {
+  constructor() {
+    this.c = 3
+    this.num = 3
+    this.arr = [7, 8, 9]
+  }
+}
+
+const collection = [Store1, Store2, Store3]
+
+export default {
+  'functional tools': {
+    'currying'() {
+      const filterTwo = filter((state) => state.num !== 2)
+      assert.isFunction(filterTwo)
+      assert.isArray(filterTwo(collection))
+
+      const mapSquare = map((state) => state.num * state.num)
+      assert.isFunction(mapSquare)
+      assert.isArray(mapSquare(collection))
+
+      const replaceState = reduce((state, nextState) => nextState)
+      assert.isFunction(replaceState)
+      assert.isObject(replaceState(collection))
+
+      const flatten = flatMap(state => state.arr)
+      assert.isFunction(flatten)
+      assert.isArray(flatten(collection))
+
+      const zip = zipWith(state => state)
+      assert.isFunction(zip)
+      assert.isArray(zip(collection, collection))
+    },
+
+    'map'() {
+      const value = map((state) => {
+        return state.num * 2
+      }, collection)
+
+      assert.deepEqual(value, [2, 4, 6])
+    },
+
+    'filter'() {
+      const value = filter((state) => {
+        return state.num === 2
+      }, collection)
+
+      assert(value[0] === Store2)
+    },
+
+    'reduce'() {
+      const value = reduce((n, nextState) => {
+        return n + nextState.num
+      }, collection, 0)
+
+      assert(value === 6)
+    },
+
+    'zipWith'() {
+      const value = zipWith((a, b) => {
+        return a.arr.concat(b.arr).reduce((n, x) => n + x, 0)
+      }, [Store1], [Store2])
+
+      assert(value[0] === 21)
+    },
+
+    'flatMap'() {
+      const value = flatMap((state) => {
+        return state.num === 2
+          ? state.num
+          : state.arr
+      }, collection)
+      assert.deepEqual(value, [1, 2, 3, 2, 7, 8, 9])
+    },
+  }
+}