From 5fbc5303ff7e8349d63f9c803d51ef141693f9e0 Mon Sep 17 00:00:00 2001
From: Mateo Calle <matecalle@gmail.com>
Date: Tue, 24 May 2016 20:05:37 -0500
Subject: [PATCH] Added _.defaultTo. (#2381)

---
 fp/_mapping.js  |  2 +-
 lodash.js       | 29 +++++++++++++++++++++++++++++
 test/test-fp.js | 36 ++++++++++++++++++++++++++++++++++++
 test/test.js    | 20 +++++++++++++++++++-
 4 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/fp/_mapping.js b/fp/_mapping.js
index a30c5dee4..2f62274a3 100644
--- a/fp/_mapping.js
+++ b/fp/_mapping.js
@@ -62,7 +62,7 @@ exports.aryMethod = {
   '2': [
     'add', 'after', 'ary', 'assign', 'assignIn', 'at', 'before', 'bind', 'bindAll',
     'bindKey', 'chunk', 'cloneDeepWith', 'cloneWith', 'concat', 'countBy', 'curryN',
-    'curryRightN', 'debounce', 'defaults', 'defaultsDeep', 'delay', 'difference',
+    'curryRightN', 'debounce', 'defaults', 'defaultsDeep', 'defaultTo', 'delay', 'difference',
     'divide', 'drop', 'dropRight', 'dropRightWhile', 'dropWhile', 'endsWith',
     'eq', 'every', 'filter', 'find', 'findIndex', 'findKey', 'findLast',
     'findLastIndex', 'findLastKey', 'flatMap', 'flatMapDeep', 'flattenDepth',
diff --git a/lodash.js b/lodash.js
index 70fd86c4c..5840049a6 100644
--- a/lodash.js
+++ b/lodash.js
@@ -14705,6 +14705,34 @@
       };
     }
 
+    /**
+     * Returns a default value if the input is `undefined`.
+     *
+     * @static
+     * @memberOf _
+     * @since 4.13.2
+     * @category Util
+     * @param {*} input The value to be checked if it is `undefined`.
+     * @param {*} defaultValue The default value that gets returned if the input is `undefined`.
+     * @returns {*} Returns the input or if it's `undefined`, the default value.
+     * @example
+     *
+     * console.log(_.defaultTo(undefined, 10));
+     * // => 10
+     *
+     * // Inside flow (FP only)
+     * var findOrDefault = _.flow([
+     *   _.find(function(number) { number > 5; }),
+     *   _.defaultTo(0)
+     * ]);
+     *
+     * findOrDefault([1,2,3]);
+     * // => 0
+     */
+    function defaultTo(value, defaultValue) {
+      return value === undefined ? defaultValue : value;
+    }
+
     /**
      * Creates a function that returns the result of invoking the given functions
      * with the `this` binding of the created function, where each successive
@@ -15979,6 +16007,7 @@
     lodash.cloneDeepWith = cloneDeepWith;
     lodash.cloneWith = cloneWith;
     lodash.deburr = deburr;
+    lodash.defaultTo = defaultTo;
     lodash.divide = divide;
     lodash.endsWith = endsWith;
     lodash.eq = eq;
diff --git a/test/test-fp.js b/test/test-fp.js
index 1fd668753..8e8ca3263 100644
--- a/test/test-fp.js
+++ b/test/test-fp.js
@@ -833,6 +833,42 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('fp.defaultTo');
+
+  (function() {
+    QUnit.test('should return a default value if input is undefined', function(assert) {
+      assert.expect(4);
+
+      // default (inverse params)
+      var actual = fp.defaultTo(0, fp.find(function(a) { return a > 1; }, [1,2,3]));
+      assert.deepEqual(actual, 2);
+
+      var actual = fp.defaultTo(0, fp.find(function(a) { return a > 5; }, [1,2,3]));
+      assert.deepEqual(actual, 0);
+
+      // curried
+      var actual = fp.defaultTo(0)(fp.find(function(a) { return a > 1; })([1,2,3]));
+      assert.deepEqual(actual, 2);
+
+      var actual = fp.defaultTo(0)(fp.find(function(a) { return a > 5; })([1,2,3]));
+      assert.deepEqual(actual, 0);
+    });
+
+    QUnit.test('should work in a flow', function(assert) {
+      assert.expect(2);
+
+      var actual = fp.flow([
+        fp.find(function(a) { return a > 3 }),
+        fp.defaultTo(0)
+      ]);
+
+      assert.deepEqual(actual([1,2,3]), 0);
+      assert.deepEqual(actual([3,4,5]), 4);
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('fp.difference');
 
   (function() {
diff --git a/test/test.js b/test/test.js
index 1006fbc5c..4da14f93b 100644
--- a/test/test.js
+++ b/test/test.js
@@ -4601,6 +4601,23 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.defaultTo');
+
+  (function() {
+    QUnit.test('should return a default value if the input is undefined', function(assert) {
+      assert.expect(3);
+
+      assert.strictEqual(_.defaultTo(1, 0), 1);
+      assert.strictEqual(_.defaultTo(undefined, 0), 0);
+
+      var actual = _.defaultTo(_.find([1,2,3], function(n) { return n > 5; }), 0);
+
+      assert.strictEqual(actual, 0);
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.defer');
 
   (function() {
@@ -26246,6 +26263,7 @@
       'ceil',
       'clone',
       'deburr',
+      'defaultTo',
       'divide',
       'endsWith',
       'escape',
@@ -26576,7 +26594,7 @@
     var acceptFalsey = lodashStable.difference(allMethods, rejectFalsey);
 
     QUnit.test('should accept falsey arguments', function(assert) {
-      assert.expect(314);
+      assert.expect(315);
 
       var arrays = lodashStable.map(falsey, stubArray);