diff --git a/src/.prettierrc b/src/.prettierrc
new file mode 100644
index 0000000..6312b3c
--- /dev/null
+++ b/src/.prettierrc
@@ -0,0 +1,5 @@
+{
+  "singleQuote": true,
+  "arrowParens": "avoid",
+  "printWidth": 120
+}
diff --git a/src/leecode/javascript/67.二进制求和.js b/src/leecode/javascript/67.二进制求和.js
index 1eb1f75..354788b 100644
--- a/src/leecode/javascript/67.二进制求和.js
+++ b/src/leecode/javascript/67.二进制求和.js
@@ -10,5 +10,19 @@
  * @param {string} b
  * @return {string}
  */
-var addBinary = function (a, b) {};
+var addBinary = function (a, b) {
+  let carry = 0,
+    index = 1,
+    ret = '';
+  while (a[a.length-index] || b[b.length-index]) {
+    const aval = parseInt(a[a.length-index] || 0);
+    const bval = parseInt(b[b.length-index] || 0);
+    ret = ((aval ^ bval) ^ carry) + ret;
+    carry = (aval & bval) | (aval & carry) | (bval & carry);
+    index ++;
+  }
+  if (carry) ret = carry + ret;
+  return ret;
+};
+console.log(addBinary('1', '11'));
 // @lc cod   e=end