Merge pull request #4655 from seegno-forks/enhancement/improve-instance-previous

Improve `previous()` instance method

changelog.md

 # NEXT
 - [FIXED] Mark unscoped model as `.scoped`, to prevent injection of default scope on includes [#4663](https://github.com/sequelize/sequelize/issues/4663)
+- [ADDED] `.previous` now returns and object of previous values when called without `key`. This brings the API in line with `.changed`
 
 # 3.12.1
 - [FIXED] Mark postgres connection as invalid if the connection is reset [#4661](https://github.com/sequelize/sequelize/pull/4661)

lib/instance.js

@@ -416,11 +416,20 @@ Instance.prototype.changed = function(key, value) {
 
 /**
  * Returns the previous value for key from `_previousDataValues`.
- * @param {String} key
- * @return {any}
+ *
+ * If called without a key, returns the previous values for all values which have changed
+ *
+ * @param {String} [key]
+ * @return {any|Array<any>}
  */
 Instance.prototype.previous = function(key) {
-  return this._previousDataValues[key];
+  if (key) {
+    return this._previousDataValues[key];
+  }
+
+  return _.pick(this._previousDataValues, function(value, key) {
+    return this.changed(key);
+  }, this);
 };
 
 Instance.prototype._setInclude = function(key, value, options) {

test/integration/instance/values.test.js

@@ -450,6 +450,23 @@ describe(Support.getTestDialectTeaser('DAO'), function() {
     });
 
     describe('previous', function() {
+      it('should return an object with the previous values', function() {
+        var User = this.sequelize.define('User', {
+          name: { type: DataTypes.STRING },
+          title: { type: DataTypes.STRING }
+        });
+
+        var user = User.build({
+          name: 'Jan Meier',
+          title: 'Mr'
+        });
+
+        user.set('name', 'Mick Hansen');
+        user.set('title', 'Dr');
+
+        expect(user.previous()).to.eql({ name: 'Jan Meier', title: 'Mr' });
+      });
+
       it('should return the previous value', function() {
         var User = this.sequelize.define('User', {
           name: {type: DataTypes.STRING}