update

Author: liuhanqu

README.md

@@ -1,2 +1,7 @@
 # leetcode
+
 LeetCode Problems' Solutions in JavaScript
+
+## easy
+
+1.  [计数质数](./easy/countPrimes/countPrimis.js)

algorithms/easy/hammingWeight/hammingWeight.js

@@ -0,0 +1,17 @@
+// description: https://leetcode-cn.com/explore/interview/card/top-interview-questions-easy/26/others/64/
+// 位1的个数
+
+/**
+ * @param {number} n - a positive integer
+ * @return {number}
+ */
+var hammingWeight = function(n) {
+  var sn = n.toString(2);
+  var count = 0;
+  for (var i = 0, len = sn.length; i < len; i++) {
+    if (sn.charAt(i) === "1") {
+      count = count + 1;
+    }
+  }
+  return count;
+};