From 0b0f6dc3760fb89c5750563fd9061b54adc69cbc Mon Sep 17 00:00:00 2001
From: Andy Brown <asbrown002@gmail.com>
Date: Mon, 17 Aug 2015 09:15:57 -0700
Subject: [PATCH] default to array when update keys are integers

---
 lib/update.js             | 10 +++-------
 lib/util/defaultObject.js | 35 +++++++++++++++++++++++++++++++++++
 lib/util/isEmpty.js       |  5 +++++
 test/updateIn-spec.js     |  6 ++++++
 test/updeep-spec.js       | 12 ++++++++++++
 5 files changed, 61 insertions(+), 7 deletions(-)
 create mode 100644 lib/util/defaultObject.js
 create mode 100644 lib/util/isEmpty.js

diff --git a/lib/update.js b/lib/update.js
index 5ea4e62..e1c3dc3 100644
--- a/lib/update.js
+++ b/lib/update.js
@@ -1,8 +1,6 @@
 import wrap from './wrap';
-
-function isEmpty(object) {
-  return !Object.keys(object).length;
-}
+import isEmpty from './util/isEmpty';
+import defaultObject from './util/defaultObject';
 
 function reduce(object, callback, initialValue) {
   return Object.keys(object).reduce((acc, key) => {
@@ -64,9 +62,7 @@ function update(updates, object, ...args) {
     return updates;
   }
 
-  const defaultedObject = (typeof object === 'undefined' || object === null) ?
-    {} :
-    object;
+  const defaultedObject = defaultObject(object, updates);
 
   const resolvedUpdates = resolveUpdates(updates, defaultedObject);
 
diff --git a/lib/util/defaultObject.js b/lib/util/defaultObject.js
new file mode 100644
index 0000000..be6286f
--- /dev/null
+++ b/lib/util/defaultObject.js
@@ -0,0 +1,35 @@
+import isEmpty from './isEmpty';
+
+function isInt(value) {
+  if (isNaN(value)) {
+    return false;
+  }
+  const x = parseFloat(value);
+  return (x | 0) === x;
+}
+
+function isArrayUpdate(updates) {
+  for (const updateKey of Object.keys(updates)) {
+    if (!isInt(updateKey)) { return false; }
+  }
+
+  return true;
+}
+
+function arrayOrObject(updates) {
+  if (!isEmpty(updates) && isArrayUpdate(updates)) {
+    return [];
+  }
+
+  return {};
+}
+
+function defaultObject(object, updates) {
+  if (typeof object === 'undefined' || object === null) {
+    return arrayOrObject(updates);
+  }
+
+  return object;
+}
+
+export default defaultObject;
diff --git a/lib/util/isEmpty.js b/lib/util/isEmpty.js
new file mode 100644
index 0000000..4e27ba2
--- /dev/null
+++ b/lib/util/isEmpty.js
@@ -0,0 +1,5 @@
+function isEmpty(object) {
+  return !Object.keys(object).length;
+}
+
+export default isEmpty;
diff --git a/test/updateIn-spec.js b/test/updateIn-spec.js
index 6c15fb3..6f9b73a 100644
--- a/test/updateIn-spec.js
+++ b/test/updateIn-spec.js
@@ -27,6 +27,12 @@ describe('u.updateIn', () => {
     expect(result).to.eql({ a: [0, 3, 0] });
   });
 
+  it('can create array if all keys are numbers', () => {
+    const result = u.updateIn('a.0', 3, null);
+
+    expect(result).to.eql({ a: [3] });
+  });
+
   it('can be partially applied', () => {
     const object = { a: { b: 0 } };
     const result = u.updateIn('a.b')(3)(object);
diff --git a/test/updeep-spec.js b/test/updeep-spec.js
index 36c17e5..bbfb4b9 100644
--- a/test/updeep-spec.js
+++ b/test/updeep-spec.js
@@ -42,6 +42,18 @@ describe('updeep', () => {
     expect(u(null, {})).to.be.null;
   });
 
+  it('can create array if all keys are numbers', () => {
+    const result = u({ 0: 'hi', '1': 'world' }, null);
+
+    expect(result).to.eql(['hi', 'world']);
+  });
+
+  it('does not create array if any key is not number', () => {
+    const result = u({ 0: 'hi', '1a': 'world' }, null);
+
+    expect(result).to.eql({ 0: 'hi', '1a': 'world' });
+  });
+
   it('can add an element to an array', () => {
     const object = [];
     const result = u({ 0: 3 }, object);