Support for extending arrays

jashkenas · Nov 28, 2011 · 83133be · 83133be
1 parent 4ce11b2
commit 83133be
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Showing 2 changed files with 5 additions and 0 deletions.
diff --git a/test/objects.js b/test/objects.js
@@ -41,6 +41,8 @@ $(document).ready(function() {
     equals(_.keys(result).join(''), 'b', 'extend does not copy undefined values');
     same(_.extend({x:'x', a:{b:'c'}}, { a: { d: 'e' } }).a, {b:'c', d:'e'}, 'can extend an object recursively when source property is a hash');
     same(_.extend({x:'x'}, { a: { b: 'c' } }).a, {b:'c'}, 'can extend an object recursively when destination does not exist');
+    same(_.extend({x:'x', a:[1,2,3]}, { a:[4] }).a, [1,2,3,4], 'can merge arrays');
+    same(_.extend({x:'x', a:{b:'c'}}, { a:[4] }).a, [4], 'overrides destination with source if types are different');
   });
 
   test("objects: defaults", function() {

diff --git a/underscore.js b/underscore.js
@@ -649,6 +649,9 @@
           if(obj[prop] != undefined && _.isObject(source[prop]) && !_.isArray(source[prop])) {
             _.extend(obj[prop], source[prop]);
           }
+          else if(_.isArray(obj[prop]) && _.isArray(source[prop])) {
+            obj[prop] = _.union(obj[prop], source[prop]);
+          }
           else {
             obj[prop] = source[prop];
           }