reduce() now too

index.js

@@ -15,6 +15,17 @@ Traverse.prototype.forEach = function (cb) {
     return this.value;
 };
 
+Traverse.prototype.reduce = function (cb, init) {
+    var skip = arguments.length === 1;
+    var acc = skip ? this.value : init;
+    this.forEach(function (x) {
+        if (!this.isRoot || !skip) {
+            acc = cb.call(this, acc, x);
+        }
+    });
+    return acc;
+};
+
 Traverse.prototype.paths = function () {
     var acc = [];
     this.forEach(function (x) {

test/mutability.js

@@ -66,3 +66,23 @@ exports.cloneT = function () {
     obj.c.push(5);
     assert.eql(res.c, [ 3, 4 ]);
 };
+
+exports.reduce = function () {
+    var obj = { a : 1, b : 2, c : [ 3, 4 ] };
+    var res = Traverse(obj).reduce(function (acc, x) {
+        if (this.isLeaf) acc.push(x);
+        return acc;
+    }, []);
+    assert.eql(obj, { a : 1, b : 2, c : [ 3, 4 ] });
+    assert.eql(res, [ 1, 2, 3, 4 ]);
+};
+
+exports.reduceInit = function () {
+    var obj = { a : 1, b : 2, c : [ 3, 4 ] };
+    var res = Traverse(obj).reduce(function (acc, x) {
+        if (this.isRoot) assert.fail('got root');
+        return acc;
+    });
+    assert.eql(obj, { a : 1, b : 2, c : [ 3, 4 ] });
+    assert.eql(res, obj);
+};