Fix hack with List.js

Author: mfix22

index.js

@@ -1,4 +1,5 @@
 const { Either, either, left, fromNullable } = require('./src/either')
+const { List } = require('./src/list')
 
 const id = _ => _
 const always = a => () => a
@@ -12,7 +13,7 @@ const DEFAULTS = {
 }
 
 /* --- Functional Utilities --- */
-const map = fn => x => (x.map ? x.map(fn) : fn(x)) // FIXME remove check
+const map = fn => x => x.map(fn)
 const join = m => m.join()
 // const chain = fn => m => m.chain(fn)
 const compose = (...fns) => (res, ...args) =>
@@ -29,6 +30,8 @@ const createRootObj = compose(
   Number
 )
 
+const handleArrays = _ => (Array.isArray(_) ? List.of(_) : Either.of(_))
+
 const normalizeField = delimiter => m =>
   fromNullable(m)
     .map(m => m.indexOf(delimiter) > -1)
@@ -96,7 +99,9 @@ class Mapper {
           .chain(getMapSpec(this.config.mapDelimiter))
           .chain(([sourceField, targetField]) =>
             Either.of(sourceField)
+              .map(handleArrays)
               .map(map(field => get(field, this.config.objDelimiter)(curr)))
+              .map(join)
               .map(_ =>
                 compose(
                   /* End user-land transforms */

src/list.js

@@ -0,0 +1,26 @@
+class List {
+  constructor(xs) {
+    this._ = xs
+    this.concat = x => new List(xs.concat(x))
+    // ----- Functor List
+    this.map = fn => new List(xs.map(fn))
+    this.chain = fn => xs.map(fn)
+    this.join = () => xs
+  }
+  // inspect() { return `List(${inspect(this._)})` }
+  // ----- Traversable List
+  // sequence(of) { return this.traverse(of, identity); }
+  // traverse(of, fn) {
+  //   return this._.reduce(
+  //     (f, a) => fn(a).map(b => bs => bs.concat(b)).ap(f),
+  //     of(new List([])),
+  //   );
+  // }
+}
+
+// ----- Pointed List
+List.of = xs => new List(xs)
+
+module.exports = {
+  List
+}