Merge pull request #142 from danheberden/pluckByArray

Add `at` method to get elements from a collection.

Former-commit-id: 99e4d651afe760f952398e5119d03c6caff0fc44

build.js

@@ -67,6 +67,7 @@
   var dependencyMap = {
     'after': [],
     'assign': ['isArguments'],
+    'at': ['isString'],
     'bind': ['isFunction', 'isObject'],
     'bindAll': ['bind', 'functions'],
     'bindKey': ['isFunction', 'isObject'],

lodash.js

@@ -1937,6 +1937,41 @@
 
   /*--------------------------------------------------------------------------*/
 
+  /**
+   * Retrieves the elements in the `collection` at specified indexes. Indexes may 
+   * be specified as individual arguments or as arrays of indexes.
+   *
+   * @static
+   * @memberOf _
+   * @category Collections
+   * @param {Array|Object|String} collection The collection to iterate over.
+   * @param {Number|Array} number|[index1, index2, ...] The index(es) of `collection`
+   *  to retrieve, either as individual arguments or arrays.
+   * @returns {Array} Returns a new array of elements that matched the provided indexes.
+   * @example
+   *
+   * _.at( ['a', 'b', 'c', 'd', 'e', 'f'], [0, 2, 5] );
+   * // => ['a', 'c', 'f']
+   *
+   * _.at( ['lodash', 'javascript', 'fast'], 0, 2 );
+   * // => ['lodash, 'fast']
+   */
+  function at(collection) {
+    var index = -1,
+        props = concat.apply(arrayRef, slice(arguments, 1)),
+        length = props.length,
+        result = Array(length);
+
+    if (noCharByIndex && isString(collection)) {
+      collection = collection.split('');
+    }
+
+    while(++index < length) {
+      result[index] = collection[props[index]];
+    }
+    return result;
+  }
+
   /**
    * Checks if a given `target` element is present in a `collection` using strict
    * equality for comparisons, i.e. `===`. If `fromIndex` is negative, it is used
@@ -4222,6 +4257,7 @@
   // add functions that return wrapped values when chaining
   lodash.after = after;
   lodash.assign = assign;
+  lodash.at = at;
   lodash.bind = bind;
   lodash.bindAll = bindAll;
   lodash.bindKey = bindKey;

test/test.js

@@ -667,6 +667,30 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.at');
+
+  (function() {
+    test('should get items in range', function() {
+      var result = _.at(['a', 'b',  1.4, 'c',  { 'foo': 'bar' }, 'd'], [0, 2, 4]);
+      deepEqual( result, ['a', 1.4, { 'foo': 'bar' } ]);
+    });
+    test('should work with an object for `collection`', function() {
+      var result = _.at({ 'a': 'apple', 'b': 'ball', 'c': 'count' }, ['a', 'c']);
+      deepEqual(result, ['apple', 'count']);
+    });
+    test('no list should return an empty array', function() {
+      deepEqual(_.at(['a', 'b', 'c']), [] );
+    });
+    test('should work on strings', function() {
+      deepEqual(_.at("helio", [0,3]), ['h', 'i']);
+    });
+    test('should work with multple args', function() {
+      deepEqual(_.at(['a','b','c','d'], 0, 2, 3), ['a', 'c', 'd']);
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.groupBy');
 
   (function() {