Update object

index.js

@@ -124,6 +124,21 @@
       return set(obj[currentPath], path.slice(1), value, doNotReplace);
     }
 
+    /**
+     * Updates an existing value using a provided function
+     * @param  {Object}       obj                   The object to modify
+     * @param  {String|Array} path                  The path of the property to modify
+     * @param  {Function}     func                  The function to apply to the existing property
+     * @param  {*}            [defaultValue]        The value to be used by the function if none exists already
+     * @return {Object}       The modified object
+     * @author Jared Rewerts <jaredrewerts@gmail.com>
+     */
+    objectPath.update = function(obj, path, func, defaultValue, modifyDefault){
+      var value = objectPath.get(obj, path, defaultValue);
+      value = func(value, obj, path);
+      return objectPath.set(obj, path, value);
+    }
+
     objectPath.has = function (obj, path) {
       if (typeof path === 'number') {
         path = [path];

test.js

@@ -237,6 +237,34 @@ describe('set', function() {
   });
 });
 
+describe('update', function() {
+  it('should update an existing array of values', function() {
+    var obj = getTestObj();
+    objectPath.update(obj, ['b', 'd'], function(value, object, path) {
+      var newValue = []
+      for (var i = 0; i < value.length; i++) {
+        newValue.push(value[i].charCodeAt(0))
+      }
+      return newValue;
+    })
+    expect(obj.b.d[0]).to.be.equal(97)
+    expect(obj.b.d[1]).to.be.equal(98)
+  });
+
+  it('should update an array of values that doesn\'t exist', function() {
+    var obj = getTestObj();
+    objectPath.update(obj, ['b', 'z'], function(value, object, path) {
+      var newValue = []
+      for (var i = 0; i < value.length; i++) {
+        newValue.push(value[i].charCodeAt(0))
+      }
+      return newValue;
+    }, ['x', 'y', 'z'])
+    expect(obj.b.z[0]).to.be.equal(120)
+    expect(obj.b.z[1]).to.be.equal(121)
+    expect(obj.b.z[2]).to.be.equal(122)
+  });
+});
 
 describe('push', function() {
   it('should push value to existing array using unicode key', function() {