diff --git a/.github/workflows b/.github/workflows
new file mode 100644
index 0000000..cacdd10
--- /dev/null
+++ b/.github/workflows
@@ -0,0 +1,29 @@
+# This workflow will do a clean installation of node dependencies, cache/restore them, build the source code and run tests across different versions of node
+# For more information see: https://help.github.com/actions/language-and-framework-guides/using-nodejs-with-github-actions
+
+name: Node.js CI
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [16.x]
+        # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v3
+      with:
+        node-version: ${{ matrix.node-version }}
+    - run: yarn
+    - run: yarn test
\ No newline at end of file
diff --git a/lib/add.js b/lib/add.js
index 1714b95..2b4b82d 100644
--- a/lib/add.js
+++ b/lib/add.js
@@ -1,5 +1,18 @@
-function add() {
-  // 实现该函数
+function add(str1, str2) {
+  let arr1 = str1.split("").map((s) => Number(s)),
+    arr2 = str2.split("").map((s) => Number(s));
+  let temp,
+    result = "",
+    sign = 0;
+
+  while (arr1.length || arr2.length || sign) {
+    temp = (arr1.pop() || 0) + (arr2.pop() || 0) + sign;
+
+    sign = Math.floor(temp / 10);
+    result = (temp % 10) + "" + result;
+  }
+
+  return result;
 }
 
-module.exports = add
\ No newline at end of file
+module.exports = add;
\ No newline at end of file
diff --git a/test/test.spec.js b/test/test.spec.js
index 935b70e..06b0335 100644
--- a/test/test.spec.js
+++ b/test/test.spec.js
@@ -4,7 +4,7 @@ describe('大数相加add方法', function () {
   test('字符串"42329"加上字符串"21532"等于"63861"', function () {
     expect(add('42329', '21532')).toBe('63861')
   })
-  
+
   test('"843529812342341234"加上"236124361425345435"等于"1079654173767686669"', function () {
     expect(add('843529812342341234', '236124361425345435')).toBe('1079654173767686669')
   })