diff --git a/solution/088.Merge Sorted Array/Solution.js b/solution/088.Merge Sorted Array/Solution.js
new file mode 100644
index 0000000000000..5079f28b336ae
--- /dev/null
+++ b/solution/088.Merge Sorted Array/Solution.js	
@@ -0,0 +1,39 @@
+//beat 88%
+const merge1 = function(nums1, m, nums2, n){
+  const arr = nums1.slice(0,m);
+  let i = 0, j = 0;
+  let count = 0;
+  while(i < m && j < n){
+    if(arr[i] <= nums2[j]){
+      nums1[count++] = arr[i++];
+    }else{
+      nums1[count++] = nums2[j++];
+    }
+  }
+  while(i < m){
+    nums1[count++] = arr[i++];
+  }
+  while(j < n){
+    nums1[count++] = nums2[j++];
+  }
+};
+
+//beat 30%....
+const merge = function(nums1, m, nums2,n){
+  let index = m + n - 1;
+  let aindex = m - 1;
+  let bindex = n - 1;
+  while(aindex >= 0 && bindex >= 0){
+    if(nums1[aindex] > nums2[bindex]){
+      nums1[index--] = nums1[aindex--];
+    }else{
+      nums1[index--] = nums2[bindex--];
+    }
+  }
+  while(aindex >= 0){
+    nums1[index--] = nums1[aindex--];
+  }
+  while(bindex >= 0){
+    nums1[index--] = nums2[bindex--];
+  }
+};
\ No newline at end of file
diff --git a/solution/204.Count Primes/Solution.js b/solution/204.Count Primes/Solution.js
new file mode 100644
index 0000000000000..babdb9910cfc9
--- /dev/null
+++ b/solution/204.Count Primes/Solution.js	
@@ -0,0 +1,31 @@
+// 600ms多
+const countPrimes2 = function(n){
+  let arr = [];
+  let res = 0;
+  for(let i = 2; i < n; i++){
+    if(arr[i] === undefined){
+      arr[i] = 1;
+      res++;
+      for(let j = 2; i * j < n; j++){
+        arr[i * j] = 0;
+      }
+    }
+  }
+  return res;
+};
+
+//200ms多
+const countPrimes = function(n){
+  let arr = [];
+  let res = 0;
+  for(let i = 2; i < n; i++){
+    if(arr[i] === undefined){
+      arr[i] = 1;
+      res++;
+      for(let j = i; i * j < n; j++){
+        arr[i * j] = 0;
+      }
+    }
+  }
+  return res;
+};
diff --git a/solution/278.First Bad Version/Solution.js b/solution/278.First Bad Version/Solution.js
new file mode 100644
index 0000000000000..09b2b5359b25b
--- /dev/null
+++ b/solution/278.First Bad Version/Solution.js	
@@ -0,0 +1,34 @@
+/**
+ * Definition for isBadVersion()
+ * 
+ * @param {integer} version number
+ * @return {boolean} whether the version is bad
+ * isBadVersion = function(version) {
+ *     ...
+ * };
+ */
+
+/**
+ * @param {function} isBadVersion()
+ * @return {function}
+ */
+const solution = function(isBadVersion) {
+  /**
+   * @param {integer} n Total versions
+   * @return {integer} The first bad version
+   */
+  return function(n) {
+      if(n === 1) return n;
+      let left = 1, right = n;
+      while(left < right){
+        let mid = left + Math.floor((right-left)/2);
+        if(isBadVersion(mid)){
+          if(mid === left) return mid;
+          else right = mid;
+        }else{
+          if(isBadVersion(mid+1)) return mid+1;
+          else left = mid + 1;
+        }
+      }
+  };
+};
\ No newline at end of file