Refactoring and tests.

.eslintrc

@@ -3,6 +3,7 @@
   "parser": "babel-eslint",
   "env": {
     "es6": true,
+    "node": true,
   },
   "parserOptions": {
     "ecmaVersion": 6,

lib/index.js

@@ -25,14 +25,23 @@ var isProps = function isProps(x) {
     return false;
   }
   var proto = protoOf(x);
-  return proto && !protoOf(proto);
+  return !!proto && !protoOf(proto);
 };
 
 var clone = function clone(data) {
   return isArray(data) ? data.slice() : Object.assign({}, data);
 };
+
 var toPathParts = function toPathParts(path) {
-  return isArray(path) ? path : (path || '').split('.');
+  if (isArray(path)) {
+    return path;
+  }
+
+  if (typeof path === 'string') {
+    return path.split('.');
+  }
+
+  return [path];
 };
 
 //---------------------------------------------------------
@@ -58,38 +67,15 @@ var PropsMatcher = function PropsMatcher(props) {
 };
 
 var Matcher = function Matcher(spec) {
-  if (isFunc(spec)) return spec;
+  if (isFunc(spec)) {
+    return spec;
+  }
   var keys = Object.keys(spec);
   return keys.length === 1 ? PropMatcher(keys[0], spec[keys[0]]) : PropsMatcher(spec);
 };
 
 //---------------------------------------------------------
 
-// const findLastIndex = (array, check) => {
-//   let i = array.length
-//   while (i--) {
-//     if (check(array[i])) {
-//       return i
-//     }
-//   }
-//   return null
-// }
-
-// const findKey = (obj, check) => {
-//   for (const key in obj) {
-//     if (check(obj[key])) {
-//       return key
-//     }
-//   }
-//   return null
-// }
-
-// export default function find (data, check) {
-//   return Array.isArray(data) ? findLastIndex(data, check) : findKey(data, check)
-// }
-
-//---------------------------------------------------------
-
 var REMOVE = exports.REMOVE = function REMOVE() {
   return REMOVE;
 };
@@ -112,35 +98,40 @@ var change = function change(key, val, data, original) {
   return target;
 };
 
+//---------------------------------------------------------
+
 var mapArray = function mapArray(array, f) {
   var n = array.length;
-  var cloned = void 0;
-  var toRemove = false;
+  var ret = array;
+  var changed = false;
+  var c = 0;
 
   for (var i = 0; i < n; ++i) {
-    var newVal = f(array[i], i, array);
-    if (newVal !== array[i]) {
-      if (!cloned) cloned = array.slice();
-      cloned[i] = newVal;
-      toRemove = toRemove || newVal === REMOVE;
+    var val = f(array[i], i, array);
+    if (!changed) {
+      if (val === array[i]) continue;
+      ret = array.slice();
+      changed = true;
+      c = i;
+    }
+    if (val !== REMOVE) {
+      ret[c++] = val;
     }
   }
 
-  if (toRemove) {
-    return cloned.filter(function (it) {
-      return it !== REMOVE;
-    });
+  if (changed && c < n) {
+    ret.length = c;
   }
 
-  return cloned || array;
+  return ret;
 };
 
 var mapProps = function mapProps(obj, f) {
   var ret = obj;
 
   for (var key in obj) {
-    var newVal = f(obj[key], key, obj);
-    ret = change(key, newVal, ret, obj);
+    var val = f(obj[key], key, obj);
+    ret = change(key, val, ret, obj);
   }
 
   return ret;
@@ -167,7 +158,7 @@ var patch = function patch(data, props) {
 };
 
 var updatePath = function updatePath(data, pathParts, update) {
-  if (pathParts.length === 0) return patch(update, data);
+  if (pathParts.length === 0) return patch(data, update);
   if (!data) return data;
 
   var _pathParts = _toArray(pathParts),
@@ -193,26 +184,15 @@ var updatePath = function updatePath(data, pathParts, update) {
   return change(part, val, data, data);
 };
 
-function update(data) {
-  var path = void 0,
-      update = void 0;
-
-  for (var _len = arguments.length, args = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
-    args[_key - 1] = arguments[_key];
-  }
-
-  if (args.length === 1) {
-    update = args[0];
-  } else {
-    path = args[0];
-    update = args[1];
+function update() {
+  switch (arguments.length) {
+    case 2:
+      return patch(arguments[0], arguments[1]);
+    case 3:
+      return updatePath(arguments[0], toPathParts(arguments[1]), arguments[2]);
+    default:
+      throw new TypeError('wrong number of arguments');
   }
-
-  if (!path) {
-    return patch(data, update);
-  }
-
-  return updatePath(data, toPathParts(path), update);
 }
 
 var remove = exports.remove = function remove(data, path) {
@@ -223,8 +203,8 @@ var remove = exports.remove = function remove(data, path) {
 
 var fp = function fp(f) {
   return function () {
-    for (var _len2 = arguments.length, args = Array(_len2), _key2 = 0; _key2 < _len2; _key2++) {
-      args[_key2] = arguments[_key2];
+    for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
+      args[_key] = arguments[_key];
     }
 
     return function (data) {