Add new function findKeys

Author: FabriceGaudin

docs/underscore.html

@@ -295,6 +295,7 @@
         <li data-name="create">- <a href="#create">create</a></li>
         <li data-name="object-functions" data-aliases="methods">- <a href="#object-functions">functions</a></li>
         <li data-name="findKey">- <a href="#findKey">findKey</a></li>
+        <li data-name="findKeys">- <a href="#findKeys">findKeys</a></li>
         <li data-name="extend">- <a href="#extend">extend</a></li>
         <li data-name="extendOwn" data-aliases="assign">- <a href="#extendOwn">extendOwn</a></li>
         <li data-name="pick">- <a href="#pick">pick</a></li>
@@ -1491,6 +1492,22 @@ <h2 id="objects">Object Functions</h2>
         to facilitate shorthand syntaxes.
       </p>
 
+      <p id="findKeys">
+        <b class="header">findKeys</b><code>_.findKeys(object, predicate, [context])</code>
+        <br />
+        Similar to <a href="#findKey"><tt>_.findKey</tt></a> but find all keys matching predicate in object.
+        Returns a new array containing all <i>keys</i> where the <b>predicate</b> truth test
+        passes.
+        <b>predicate</b> is transformed through <a href="#iteratee"><b>iteratee</b></a>
+        to facilitate shorthand syntaxes.
+      </p>
+      <pre>
+_.findKeys({moe: 39.1, larry: 23.3, curly: 35.2}, function(value, key, object) {
+  return value > 30;
+});
+=&gt; ["moe", "curly"]
+</pre>
+
       <p id="extend">
         <b class="header">extend</b><code>_.extend(destination, *sources)</code>
         <br />
@@ -1970,7 +1987,7 @@ <h2 id="utility">Utility Functions</h2>
         The following Underscore methods transform their predicates through
         <tt>_.iteratee</tt>: <tt>countBy</tt>, <tt>every</tt>,
         <tt>filter</tt>, <tt>find</tt>, <tt>findIndex</tt>, <tt>findKey</tt>,
-        <tt>findLastIndex</tt>, <tt>groupBy</tt>, <tt>indexBy</tt>,
+        <tt>findKeys</tt>, <tt>findLastIndex</tt>, <tt>groupBy</tt>, <tt>indexBy</tt>,
         <tt>map</tt>, <tt>mapObject</tt>, <tt>max</tt>, <tt>min</tt>,
         <tt>partition</tt>, <tt>reject</tt>, <tt>some</tt>, <tt>sortBy</tt>,
         <tt>sortedIndex</tt>, and <tt>uniq</tt>

index.html

@@ -111,7 +111,7 @@
       'findIndex', 'findLastIndex'
     ];
     var object = [
-      'mapObject', 'findKey', 'pick', 'omit'
+      'mapObject', 'findKey', 'findKeys', 'pick', 'omit'
     ];
 
     _.each(collection.concat(array), function(method) {

test/collections.js

@@ -718,6 +718,7 @@
     assert.strictEqual(_.find(collection, /b/g), 'bar');
     assert.strictEqual(_.findIndex(collection, /b/g), 1);
     assert.strictEqual(_.findKey(collection, /b/g), '1');
+    assert.deepEqual(_.findKeys(collection, /b/g), ['1', '2']);
     assert.strictEqual(_.findLastIndex(collection, /b/g), 2);
     assert.deepEqual(_.groupBy(collection, /b/g), {0: ['foo'], 1: ['bar'], 2: ['bbiz']});
     assert.deepEqual(_.indexBy(collection, /b/g), {0: 'foo', 1: 'bar', 2: 'bbiz'});

test/functions.js

@@ -1097,6 +1097,47 @@
     assert.strictEqual(_.findKey(array, function(x) { return x === 55; }), 'match', 'matches array-likes keys');
   });
 
+  QUnit.test('findKeys', function(assert) {
+    var objects = {
+      a: {a: 0, b: 0},
+      b: {a: 1, b: 1},
+      c: {a: 2, b: 2},
+      d: {a: 1, b: 4}
+    };
+
+    assert.deepEqual(_.findKeys(objects, function(obj) {
+      return obj.a === 0;
+    }), ['a']);
+
+    assert.deepEqual(_.findKeys(objects, function(obj) {
+      return obj.b * obj.a === 4;
+    }), ['c', 'd']);
+
+    assert.deepEqual(_.findKeys(objects, 'a'), ['b', 'c', 'd'], 'Uses lookupIterator');
+
+    assert.deepEqual(_.findKeys(objects, function(obj) {
+      return obj.b * obj.a === 5;
+    }), []);
+
+    assert.deepEqual(_.findKeys([1, 2, 3, 4, 5, 6], function(obj) {
+      return obj === 3;
+    }), ['2'], 'Keys are strings');
+
+    assert.deepEqual(_.findKeys(objects, function(a) {
+      return a.foo === null;
+    }), []);
+
+    _.findKeys({a: {a: 1}}, function(a, key, obj) {
+      assert.strictEqual(key, 'a');
+      assert.deepEqual(obj, {a: {a: 1}});
+      assert.strictEqual(this, objects, 'called with context');
+    }, objects);
+
+    var array = [1, 2, 3, 4];
+    array.match = 55;
+    assert.deepEqual(_.findKeys(array, function(x) { return x === 55; }), ['match'], 'matches array-likes keys');
+  });
+
 
   QUnit.test('mapObject', function(assert) {
     var obj = {a: 1, b: 2};

test/objects.js

@@ -1100,6 +1100,16 @@
     }
   };
 
+  // Returns an array of all keys on an object that pass a predicate test.
+  _.findKeys = function(obj, predicate, context) {
+    predicate = cb(predicate, context);
+    var allKeys = _.keys(obj), res = [];
+    _.each(allKeys, function(key) {
+      if (predicate(obj[key], key, obj)) res.push(key);
+    });
+    return res;
+  };
+
   // Internal pick helper function to determine if `obj` has key `key`.
   var keyInObj = function(value, key, obj) {
     return key in obj;