diff --git a/.idea/vcs.xml b/.idea/vcs.xml
new file mode 100644
index 0000000..94a25f7
--- /dev/null
+++ b/.idea/vcs.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
index f52bbce..751b943 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,14 +1,11 @@
 language: node_js
 node_js:
   - "6"
-
 addons:
   chrome: stable
-
-before_script:
-  - "export DISPLAY=:99.0"
-  - "sh -e /etc/init.d/xvfb start"
-  - sleep 3 # give xvfb some time to start
-
+services:
+  - xvfb
 before_install:
-  npm install karma-cli -g
\ No newline at end of file
+  npm install karma-cli -g
+script:
+  - npm run start
diff --git a/js/list.js b/js/list.js
index 356bcf9..6b8a01b 100755
--- a/js/list.js
+++ b/js/list.js
@@ -1,34 +1,35 @@
-/**
- * List
- * @author donaldyang
- */
-
-function List(head, tail) {
-	this.head = head || 0;
-	this.tail = tail || null;
-}
-
-// Returns a new List containing the array.
-List.list = function (array) {
-	var sentinel = new List(),
-		len = array.length,
-		p, i;
-
-	p = sentinel;
-	for (i = 0; i < len; i++) {
-		p.tail = new List(array[i]);
-		p = p.tail;
-	}
-	return sentinel.tail;
-}
-
-// Returns a readable String for THIS.
-List.prototype.toString = function () {
-	var res = '', L;
-	res += '[';
-	for (L = this; L !== null; L = L.tail) {
-		res = res + ' ' + L.head;
-	}
-	res += ' ]';
-	return res;
-};
+/**
+ * List
+ * @author donaldyang
+ */
+
+function List(head, tail) {
+	this.head = head || 0;
+	this.tail = tail || null;
+}
+
+// Returns a new List containing the array. [4, 6, 7, 3, 8]
+List.list = function (array) {
+	var sentinel = new List(),
+		len = array.length,
+		p, i;
+
+	p = sentinel;
+	for (i = 0; i < len; i++) {
+		p.tail = new List(array[i]);
+		p = p.tail;
+	}
+	return sentinel.tail;
+};
+
+// Returns a readable String for THIS.
+List.prototype.toString = function () {
+	var res = '', L;
+	res += '[';
+	for (L = this; L !== null; L = L.tail) {
+		res = res + ' ' + L.head;
+	}
+	res += ' ]';
+	return res;
+};
+
diff --git a/package.json b/package.json
index e80646a..da4fdf8 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,8 @@
   "description": "test",
   "main": "index.js",
   "scripts": {
-    "test": "karma start"
+    "test": "karma start",
+    "start": "karma start --single-run"
   },
   "repository": {
     "type": "git",
diff --git a/quz/quz.js b/quz/quz.js
index 624e7de..443bba2 100755
--- a/quz/quz.js
+++ b/quz/quz.js
@@ -1,27 +1,48 @@
-/**
- * dcate
- * A list consisting of elements of A followed by the
- * elements of B. May modify items of A.
- * Don't use 'new'
- * @param {List} A
- * @param {List} B
- * @returns {List}
- */
-function dcate(A, B) {
-	/** Fill in here **/
-}
-
-/**
- * sub
- * The sublist consisting of LEN items from list L,
- * beginning with item #START (where the first item is #0).
- * Does not modify the original list elements.
- * it is an error if the desired items don't exist.
- * @param {List} L
- * @param {Number} start
- * @param {Number} len
- * @returns {List}
- */
-function sub(L, start, len) {
-	/** Fill in here **/
-}
+/**
+ * dcate
+ * A list consisting of elements of A followed by the
+ * elements of B. May modify items of A.
+ * Don't use 'new'
+ * @param {List} A
+ * @param {List} B
+ * @returns {List}
+ */
+// var A = List.list([4, 6, 7, 3, 8]),
+// 	B = List.list([3, 2, 5, 9]),
+// 	C = List.list([19, 8, 7, 3, 2]);
+function dcate(A, B) {
+	let p = A;
+	// p：A中的最末尾元素
+	while (p.tail) {
+		p = p.tail
+	}
+	// 将B添加到A的尾巴
+	p.tail = B;
+	return A
+}
+
+/**
+ * sub
+ * The sublist consisting of LEN items from list L,
+ * beginning with item #START (where the first item is #0).
+ * Does not modify the original list elements.
+ * it is an error if the desired items don't exist.
+ * @param {List} L
+ * @param {Number} start
+ * @param {Number} len
+ * @returns {List}
+ */
+function sub(L, start, len) {
+	let p = L; // 当前遍历的元素
+	let i = 0; // 第N个元素
+	let array = [];
+	while (p && p.head) {
+		// 当元素处于开始到结束之间，array增加head属性
+		if (i >= start && i <= start + len) {
+			array.push(p.head)
+		}
+		p = p.tail;
+		i++
+	}
+	return List.list(array)
+}