Uniform flatten

README.md

@@ -158,3 +158,30 @@ flatten({
 //   'key3.a': { b: { c: 2 } }
 // }
 ```
+
+### uniformFlatten
+
+If maxDepth is set, will flatten each object in the collection to the depth specified by maxDepth. This uniformly flattens the object at the depth specified.
+
+This is usually set in combination with the maxDepth option.
+
+``` javascript
+var flatten = require('flat')
+
+flatten({
+    key1: {
+        keyA: {a: 'valueI'}
+    },
+    key2: {
+        keyB: {a: {b: 'valueII'}}
+    },
+    key3: { a: { b: { c: 2 } } }
+}, { maxDepth: 2,  uniformFlatten: true})
+
+
+//{ 
+//   'key1.keyA.a': 'valueI',
+//   'key2.keyB.a': { b: 'valueII' },
+//   'key3.a.b': { c: 2 } 
+//}
+```

index.js

@@ -7,11 +7,11 @@ function flatten(target, opts) {
 
   var delimiter = opts.delimiter || '.'
   var maxDepth = opts.maxDepth
-  var currentDepth = 1
-  var output = {}
-
-  function step(object, prev) {
-    Object.keys(object).forEach(function(key) {
+  var output = {};
+  var numberToFlatten = 1;
+  function step(object, prev, currentDepth) {
+    currentDepth = currentDepth || 1;
+    Object.keys(object).forEach(function(key) { 
       var value = object[key]
       var isarray = opts.safe && Array.isArray(value)
       var type = Object.prototype.toString.call(value)
@@ -26,19 +26,20 @@ function flatten(target, opts) {
         : key
 
       if (!opts.maxDepth) {
-        maxDepth = currentDepth + 1;
+        maxDepth = numberToFlatten + 1;
       }
 
-      if (!isarray && !isbuffer && isobject && Object.keys(value).length && currentDepth < maxDepth) {
-        ++currentDepth
-        return step(value, newKey)
+      var flattenCondition = (opts.uniformFlatten) ? currentDepth : numberToFlatten
+      if (!isarray && !isbuffer && isobject && Object.keys(value).length && flattenCondition < maxDepth) {
+        ++numberToFlatten;
+        return step(value, newKey, currentDepth + 1)
       }
-
+      
       output[newKey] = value
     })
   }
 
-  step(target)
+  step(target);
 
   return output
 }

test/test.js

@@ -154,7 +154,29 @@ suite('Flatten', function() {
       }
     })
   })
-})
+
+  test('Uniform Flatten with Depth', function(){
+    assert.deepEqual(flatten({
+      hello: {
+          world: {again: 'good morning'}
+      },
+      salut: {
+          monde: {encore: {bonne: 'matin'}}
+      },
+      konnichiwa: { sekai: { mou: { ohayou: 'gozaimasu' } } }
+    }, { 
+      maxDepth: 3,  
+      uniformFlatten: true
+    }),
+    { 
+      'hello.world.again': 'good morning',
+      'salut.monde.encore': { bonne: 'matin' },
+      'konnichiwa.sekai.mou': { ohayou: 'gozaimasu' } 
+    });
+  })
+});
+
+
 
 suite('Unflatten', function() {
   test('Nested once', function() {