diff --git a/package.json b/package.json
index 594a6f6..a8aee59 100644
--- a/package.json
+++ b/package.json
@@ -2,11 +2,15 @@
   "name": "@odata/parser",
   "version": "0.1.34",
   "description": "OData(v4) Parser",
-  "main": "lib/parser.js",
-  "typings": "lib/parser.d.ts",
+  "main": "lib/index",
+  "typings": "lib/index.d.ts",
   "engines": {
     "node": ">=10"
   },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/Soontao/odata-v4-parser"
+  },
   "contributors": [
     {
       "name": "Theo Sun",
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..447c63c
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,7 @@
+import { Parser } from './parser';
+
+export * from './parser';
+export * from './lexer';
+export * from './visitor';
+
+export const defaultParser = new Parser();
diff --git a/src/parser.ts b/src/parser.ts
index 3e9c901..7281fe8 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -21,7 +21,16 @@ export const parserFactory = function(fn) {
   };
 };
 
+/**
+ * odata uri parser
+ */
 export class Parser {
+  /**
+   * parser ast node with full odata uri
+   *
+   * @param source
+   * @param options
+   */
   odataUri(source: string, options?: any): Lexer.Token {
     return parserFactory(ODataUri.odataUri)(source, options);
   }
diff --git a/src/utils.ts b/src/utils.ts
index 7e0a648..69c028d 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,6 +1,5 @@
 import { Token, TokenType } from './lexer';
-import { forEach, isArray } from '@newdash/newdash';
-import { isPlainObject } from '@newdash/newdash/isPlainObject';
+import { createTraverser } from './visitor';
 
 export type SourceArray = number[] | Uint16Array;
 
@@ -35,30 +34,10 @@ export function required(value: SourceArray, index: number, comparer: Function,
   return i >= (min || 0) && i <= max ? index + i : 0;
 }
 
-export type Traverser = { [key in TokenType]?: (token: Token) => void }
-
-export function createTraverser(traverser: Traverser) {
-  return function t(node: Token | Array<any> | Object): void {
-
-    if (node instanceof Token) {
-      if (node.type in traverser) {
-        traverser[node.type](node);
-      }
-    }
-
-    if (isPlainObject(node) || isArray(node) || node instanceof Token) {
-      // @ts-ignore
-      forEach(node, (item) => {
-        t(item);
-      });
-    }
-
-
-  };
-}
 
 /**
- * find one node by type
+ * find one node in ast node by type
+ *
  * @param node
  * @param type
  */
@@ -69,7 +48,8 @@ export function findOne(node: Token, type: TokenType): Token {
 }
 
 /**
- * find all nodes by type
+ * find all nodes in ast node by type
+ *
  * @param node
  * @param type
  */
diff --git a/src/visitor.ts b/src/visitor.ts
new file mode 100644
index 0000000..8792f42
--- /dev/null
+++ b/src/visitor.ts
@@ -0,0 +1,44 @@
+import { TokenType, Token } from './lexer';
+import { isPlainObject } from '@newdash/newdash/isPlainObject';
+import { forEach } from '@newdash/newdash/forEach';
+import { isArray } from '@newdash/newdash/isArray';
+
+/**
+ * AST Traverser
+ */
+export type Traverser = { [key in TokenType]?: (token: Token) => void }
+
+/**
+ * AST Visitor
+ *
+ * @alias Traverser
+ */
+export type Visitor = Traverser
+
+/**
+ * Traverse AST with traverser
+ *
+ * @param traverser
+ * @param node
+ */
+export function traverseAst(traverser: Traverser, node: Token | Array<any> | Object): void {
+
+  if (node instanceof Token) {
+    if (node.type in traverser) {
+      traverser[node.type](node);
+    }
+  }
+
+  if (isPlainObject(node) || isArray(node) || node instanceof Token) {
+    // @ts-ignore
+    forEach(node, (item) => {
+      traverseAst(traverser, item);
+    });
+  }
+}
+
+export function createTraverser(traverser: Traverser) {
+  return function t(node: Token | Array<any> | Object): void {
+    traverseAst(traverser, node);
+  };
+}
diff --git a/test/visitor.spec.ts b/test/visitor.spec.ts
new file mode 100644
index 0000000..b8f048c
--- /dev/null
+++ b/test/visitor.spec.ts
@@ -0,0 +1,44 @@
+import { defaultParser, createTraverser } from '../src';
+
+describe('Visitor Parse Suite', () => {
+
+  const createSeqTokenProcessor = (key: string, arr: Array<any>) => () => arr.push(key);
+
+  const createSeqTraverser = () => {
+    const visitSequence = [];
+
+    const visit = createTraverser({
+      Top: createSeqTokenProcessor('param:top', visitSequence),
+      Skip: createSeqTokenProcessor('param:skip', visitSequence),
+      Filter: createSeqTokenProcessor('param:filter', visitSequence),
+      OrderBy: createSeqTokenProcessor('param:orderby', visitSequence),
+      Format: createSeqTokenProcessor('param:format', visitSequence),
+      Search: createSeqTokenProcessor('param:search', visitSequence),
+      InlineCount: createSeqTokenProcessor('param:inlinecount', visitSequence),
+
+      AndExpression: createSeqTokenProcessor('and', visitSequence),
+      BoolParenExpression: createSeqTokenProcessor('paren', visitSequence),
+      EqualsExpression: createSeqTokenProcessor('eq', visitSequence),
+      Literal: createSeqTokenProcessor('lit', visitSequence),
+      FirstMemberExpression: createSeqTokenProcessor('mem', visitSequence)
+    });
+
+    return { visit, visitSequence };
+  };
+
+
+  it('should visit filter', () => {
+
+    const expectedSeq = ['and', 'paren', 'eq', 'mem', 'lit', 'paren', 'eq', 'mem', 'lit'];
+
+    const { visit, visitSequence } = createSeqTraverser();
+
+    const node = defaultParser.filter('(A eq 2) and (V eq 3)');
+
+    visit(node);
+
+    expect(visitSequence).toEqual(expectedSeq);
+
+  });
+
+});