Update 204-count-primes.js

Author: everthis

204-count-primes.js

@@ -1,3 +1,28 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+const countPrimes = function(n) {
+  const arr = Array(n).fill(0)
+  
+  for(let i = 2; i * i < n; i++) {
+    if(arr[i] !== 0) continue
+    let j = i * i
+    while(j < n) {
+      arr[j] = 1
+      j += i
+    }
+  }
+  
+  let res = 0
+  for(let i = 2; i < n; i++) {
+    if(arr[i] === 0) res++
+  }
+  return res
+};
+
+// another
+
 /**
  * @param {number} n
  * @return {number}